init repo

lab3/src/main/scala/board/basys3/BCD2Segments.scala

@@ -0,0 +1,54 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package board.basys3
+
+import chisel3._
+import chisel3.util._
+
+class BCD2Segments extends Module {
+  val io = IO(new Bundle {
+    val bcd = Input(UInt(4.W))
+    val segs = Output(UInt(8.W))
+  })
+
+  val bcd = io.bcd
+  val segs = Wire(UInt(8.W))
+
+  segs := MuxLookup(
+    bcd,
+    0xFF.U,
+    IndexedSeq(
+      0.U -> "b10000001".U,
+      1.U -> "b11001111".U,
+      2.U -> "b10010010".U,
+      3.U -> "b10000110".U,
+      4.U -> "b11001100".U,
+      5.U -> "b10100100".U,
+      6.U -> "b10100000".U,
+      7.U -> "b10001111".U,
+      8.U -> "b10000000".U,
+      9.U -> "b10000100".U,
+      10.U -> "b00001000".U,
+      11.U -> "b01100000".U,
+      12.U -> "b00110001".U,
+      13.U -> "b01000010".U,
+      14.U -> "b00110000".U,
+      15.U -> "b00111000".U,
+    )
+  )
+
+  io.segs := segs
+}
+

lab3/src/main/scala/board/basys3/OnboardDigitDisplay.scala

@@ -0,0 +1,32 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package board.basys3
+
+import chisel3._
+
+class OnboardDigitDisplay extends Module {
+  val io = IO(new Bundle {
+    val digit_mask = Output(UInt(4.W))
+  })
+
+  val counter = RegInit(UInt(16.W), 0.U)
+  val digit_mask = RegInit(UInt(4.W), "b0111".U)
+
+  counter := counter + 1.U
+  when(counter === 0.U) {
+    digit_mask := (digit_mask << 1.U).asUInt + digit_mask(3)
+  }
+  io.digit_mask := digit_mask
+}

lab3/src/main/scala/board/basys3/SYSULogo.scala

@@ -0,0 +1,34 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package board.basys3
+
+import chisel3._
+import chisel3.util._
+
+class SYSULogo extends Module {
+  val io = IO(new Bundle {
+    val digit_mask = Input(UInt(4.W))
+    val segs = Output(UInt(8.W))
+  })
+
+  io.segs := MuxLookup(
+    io.digit_mask,
+    "b00100100".U, // "b0111".U, "b1101".U -> S
+    IndexedSeq(
+      "b1011".U -> "b01000100".U, // Y
+      "b1110".U -> "b01000001".U, // U
+    )
+  )
+}

lab3/src/main/scala/board/basys3/SegmentMux.scala

@@ -0,0 +1,42 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package board.basys3
+
+import chisel3._
+import chisel3.util._
+
+class SegmentMux extends Module {
+  val io = IO(new Bundle {
+    val digit_mask = Input(UInt(4.W))
+    val numbers = Input(UInt(16.W))
+    val segs = Output(UInt(8.W))
+  })
+
+
+  val digit = RegInit(UInt(4.W), 0.U)
+  val bcd2segs = Module(new BCD2Segments)
+
+  bcd2segs.io.bcd := digit
+  io.segs := bcd2segs.io.segs
+  digit := MuxLookup(
+    io.digit_mask,
+    io.numbers(3, 0), // "b1110".U
+    IndexedSeq(
+      "b1101".U -> io.numbers(7, 4),
+      "b1011".U -> io.numbers(11, 8),
+      "b0111".U -> io.numbers(15, 12)
+    )
+  )
+}

lab3/src/main/scala/board/basys3/Top.scala

@@ -0,0 +1,128 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package board.basys3
+
+import chisel3._
+import chisel3.stage.{ChiselGeneratorAnnotation, ChiselStage}
+import chisel3.util._
+import peripheral._
+import riscv._
+import riscv.core.CPU
+
+class Top extends Module {
+  val binaryFilename = "tetris.asmbin"
+  val io = IO(new Bundle {
+    val switch = Input(UInt(16.W))
+
+    val segs = Output(UInt(8.W))
+    val digit_mask = Output(UInt(4.W))
+
+    val hsync = Output(Bool())
+    val vsync = Output(Bool())
+    val rgb = Output(UInt(12.W))
+    val led = Output(UInt(16.W))
+
+    val tx = Output(Bool())
+    val rx = Input(Bool())
+
+  })
+
+  val mem = Module(new Memory(Parameters.MemorySizeInWords))
+  val display = Module(new VGADisplay)
+  val timer = Module(new Timer)
+  val uart = Module(new Uart(frequency = 100000000, baudRate = 115200))
+  val dummy = Module(new Dummy)
+
+  display.io.bundle <> dummy.io.bundle
+  mem.io.bundle <> dummy.io.bundle
+  mem.io.debug_read_address := 0.U
+  timer.io.bundle <> dummy.io.bundle
+  uart.io.bundle <> dummy.io.bundle
+  io.tx := uart.io.txd
+  uart.io.rxd := io.rx
+
+  val instruction_rom = Module(new InstructionROM(binaryFilename))
+  val rom_loader = Module(new ROMLoader(instruction_rom.capacity))
+
+  rom_loader.io.rom_data := instruction_rom.io.data
+  rom_loader.io.load_address := Parameters.EntryAddress
+  instruction_rom.io.address := rom_loader.io.rom_address
+
+  val CPU_clkdiv = RegInit(UInt(2.W), 0.U)
+  val CPU_tick = Wire(Bool())
+  val CPU_next = Wire(UInt(2.W))
+  CPU_next := Mux(CPU_clkdiv === 3.U, 0.U, CPU_clkdiv + 1.U)
+  CPU_tick := CPU_clkdiv === 0.U
+  CPU_clkdiv := CPU_next
+
+  withClock(CPU_tick.asClock) {
+    val cpu = Module(new CPU(ImplementationType.FiveStageStall))
+    cpu.io.interrupt_flag := Cat(uart.io.signal_interrupt, timer.io.signal_interrupt)
+    cpu.io.debug_read_address := 0.U
+    cpu.io.instruction_valid := rom_loader.io.load_finished
+    mem.io.instruction_address := cpu.io.instruction_address
+    cpu.io.instruction := mem.io.instruction
+
+    when(!rom_loader.io.load_finished) {
+      rom_loader.io.bundle <> mem.io.bundle
+      cpu.io.memory_bundle.read_data := 0.U
+    }.otherwise {
+      rom_loader.io.bundle.read_data := 0.U
+      when(cpu.io.device_select === 4.U) {
+        cpu.io.memory_bundle <> timer.io.bundle
+      }.elsewhen(cpu.io.device_select === 2.U) {
+        cpu.io.memory_bundle <> uart.io.bundle
+      }.elsewhen(cpu.io.device_select === 1.U) {
+        cpu.io.memory_bundle <> display.io.bundle
+      }.otherwise {
+        cpu.io.memory_bundle <> mem.io.bundle
+      }
+    }
+  }
+
+  io.hsync := display.io.hsync
+  io.vsync := display.io.vsync
+
+  io.rgb := display.io.rgb
+
+  mem.io.debug_read_address := io.switch(15, 1).asUInt << 2
+  io.led := Mux(
+    io.switch(0),
+    mem.io.debug_read_data(31, 16).asUInt,
+    mem.io.debug_read_data(15, 0).asUInt,
+  )
+
+  val onboard_display = Module(new OnboardDigitDisplay)
+  io.digit_mask := onboard_display.io.digit_mask
+
+  val sysu_logo = Module(new SYSULogo)
+  sysu_logo.io.digit_mask := io.digit_mask
+
+  val seg_mux = Module(new SegmentMux)
+  seg_mux.io.digit_mask := io.digit_mask
+  seg_mux.io.numbers := io.led
+
+  io.segs := MuxLookup(
+    io.switch,
+    seg_mux.io.segs,
+    IndexedSeq(
+      0.U -> sysu_logo.io.segs
+    )
+  )
+}
+
+object VerilogGenerator extends App {
+  (new ChiselStage).execute(Array("-X", "verilog", "-td", "verilog/basys3"), Seq(ChiselGeneratorAnnotation(() => new Top)))
+}

lab3/src/main/scala/board/pynq/Top.scala

@@ -0,0 +1,103 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package board.pynq
+
+import chisel3._
+import chisel3.stage.{ChiselGeneratorAnnotation, ChiselStage}
+import chisel3.util.Cat
+import peripheral._
+import riscv.core.CPU
+import riscv.{ImplementationType, Parameters}
+
+class Top extends Module {
+  val binaryFilename = "tetris.asmbin"
+  val io = IO(new Bundle() {
+    val hdmi_clk_n = Output(Bool())
+    val hdmi_clk_p = Output(Bool())
+    val hdmi_data_n = Output(UInt(3.W))
+    val hdmi_data_p = Output(UInt(3.W))
+    val hdmi_hpdn = Output(Bool())
+
+    val tx = Output(Bool())
+    val rx = Input(Bool())
+
+    val led = Output(UInt(4.W))
+  })
+  val mem = Module(new Memory(Parameters.MemorySizeInWords))
+  val display = Module(new HDMIDisplay)
+  val timer = Module(new Timer)
+  val uart = Module(new Uart(frequency = 125000000, baudRate = 115200))
+  val dummy = Module(new Dummy)
+
+  display.io.bundle <> dummy.io.bundle
+  mem.io.bundle <> dummy.io.bundle
+  mem.io.debug_read_address := 0.U
+  timer.io.bundle <> dummy.io.bundle
+  uart.io.bundle <> dummy.io.bundle
+  io.tx := uart.io.txd
+  uart.io.rxd := io.rx
+
+  val instruction_rom = Module(new InstructionROM(binaryFilename))
+  val rom_loader = Module(new ROMLoader(instruction_rom.capacity))
+
+  rom_loader.io.rom_data := instruction_rom.io.data
+  rom_loader.io.load_address := Parameters.EntryAddress
+  instruction_rom.io.address := rom_loader.io.rom_address
+
+  val CPU_clkdiv = RegInit(UInt(2.W), 0.U)
+  val CPU_tick = Wire(Bool())
+  val CPU_next = Wire(UInt(2.W))
+  CPU_next := Mux(CPU_clkdiv === 3.U, 0.U, CPU_clkdiv + 1.U)
+  CPU_tick := CPU_clkdiv === 0.U
+  CPU_clkdiv := CPU_next
+
+  withClock(CPU_tick.asClock) {
+    val cpu = Module(new CPU(implementation = ImplementationType.FiveStageStall))
+    val instruction_valid = RegNext(rom_loader.io.load_finished)
+    cpu.io.interrupt_flag := Cat(uart.io.signal_interrupt, timer.io.signal_interrupt)
+    cpu.io.debug_read_address := 0.U
+    cpu.io.instruction_valid := instruction_valid
+    mem.io.instruction_address := cpu.io.instruction_address
+    cpu.io.instruction := mem.io.instruction
+
+    when(!rom_loader.io.load_finished) {
+      rom_loader.io.bundle <> mem.io.bundle
+      cpu.io.memory_bundle.read_data := 0.U
+    }.otherwise {
+      rom_loader.io.bundle.read_data := 0.U
+      when(cpu.io.device_select === 4.U) {
+        cpu.io.memory_bundle <> timer.io.bundle
+      }.elsewhen(cpu.io.device_select === 2.U) {
+        cpu.io.memory_bundle <> uart.io.bundle
+      }.elsewhen(cpu.io.device_select === 1.U) {
+        cpu.io.memory_bundle <> display.io.bundle
+      }.otherwise {
+        cpu.io.memory_bundle <> mem.io.bundle
+      }
+    }
+  }
+
+  io.led := 15.U(4.W)
+
+  io.hdmi_hpdn := 1.U
+  io.hdmi_data_n := display.io.TMDSdata_n
+  io.hdmi_data_p := display.io.TMDSdata_p
+  io.hdmi_clk_n := display.io.TMDSclk_n
+  io.hdmi_clk_p := display.io.TMDSclk_p
+}
+
+object VerilogGenerator extends App {
+  (new ChiselStage).execute(Array("-X", "verilog", "-td", "verilog/pynq"), Seq(ChiselGeneratorAnnotation(() => new Top)))
+}

lab3/src/main/scala/board/verilator/Top.scala

@@ -0,0 +1,42 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package board.verilator
+
+import chisel3._
+import chisel3.stage.{ChiselGeneratorAnnotation, ChiselStage}
+import riscv.ImplementationType
+import riscv.core.{CPU, CPUBundle}
+
+class Top extends Module {
+  val io = IO(new CPUBundle)
+
+  val cpu = Module(new CPU(implementation = ImplementationType.ThreeStage))
+
+  io.device_select := 0.U
+  cpu.io.debug_read_address := io.debug_read_address
+  io.debug_read_data := cpu.io.debug_read_data
+
+  io.memory_bundle <> cpu.io.memory_bundle
+  io.instruction_address := cpu.io.instruction_address
+  cpu.io.instruction := io.instruction
+
+  cpu.io.interrupt_flag := io.interrupt_flag
+  cpu.io.instruction_valid := io.instruction_valid
+}
+
+object VerilogGenerator extends App {
+  (new ChiselStage).execute(Array("-X", "verilog", "-td", "verilog/verilator"), Seq(ChiselGeneratorAnnotation(() =>
+    new Top())))
+}

lab3/src/main/scala/peripheral/Dummy.scala

@@ -0,0 +1,29 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package peripheral
+
+import chisel3._
+import riscv.Parameters
+
+// A dummy master that never initiates reads or writes
+class Dummy extends Module {
+  val io = IO(new Bundle {
+    val bundle = Flipped(new RAMBundle)
+  })
+  io.bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(false.B))
+  io.bundle.write_data := 0.U
+  io.bundle.write_enable := false.B
+  io.bundle.address := 0.U
+}

lab3/src/main/scala/peripheral/FontROM.scala

@@ -0,0 +1,64 @@
+package peripheral
+
+import chisel3.experimental.{ChiselAnnotation, annotate}
+import chisel3.util.experimental.loadMemoryFromFileInline
+import chisel3.{Bundle, Input, Module, Output, SyncReadMem, UInt, _}
+import firrtl.annotations.MemorySynthInit
+
+import java.io.FileWriter
+import java.nio.file.Paths
+import javax.imageio.ImageIO
+
+class FontROM(fontBitmapFilename: String = "vga_font_8x16.bmp") extends Module {
+  val glyphWidth = GlyphInfo.glyphWidth
+  val glyphHeight = GlyphInfo.glyphHeight
+
+  val io = IO(new Bundle {
+    val glyph_index = Input(UInt(7.W))
+    val glyph_y = Input(UInt(4.W))
+
+    val glyph_pixel_byte = Output(UInt(8.W))
+  })
+
+  annotate(new ChiselAnnotation {
+    override def toFirrtl =
+      MemorySynthInit
+  })
+
+  val (hexTxtPath, glyphCount) = readFontBitmap()
+  val mem = SyncReadMem(glyphCount, UInt(8.W))
+  loadMemoryFromFileInline(mem, hexTxtPath.toString.replaceAll("\\\\", "/"))
+  io.glyph_pixel_byte := mem.read(io.glyph_index * GlyphInfo.glyphHeight.U + io.glyph_y, true.B)
+
+  def readFontBitmap() = {
+    val inputStream = getClass.getClassLoader.getResourceAsStream(fontBitmapFilename)
+    val image = ImageIO.read(inputStream)
+
+    val glyphColumns = image.getWidth() / glyphWidth
+    val glyphRows = image.getHeight / glyphHeight
+    val glyphCount = glyphColumns * glyphRows
+    val glyphs = new Array[UInt](glyphCount * GlyphInfo.glyphHeight)
+
+    for (row <- 0 until glyphRows) {
+      for (col <- 0 until glyphColumns) {
+        for (i <- 0 until glyphHeight) {
+          var lineInt = 0
+          for (j <- 0 until glyphWidth) {
+            if (image.getRGB(col * glyphWidth + j, row * glyphHeight + i) != 0xFFFFFFFF) {
+              lineInt |= (1 << j)
+            }
+          }
+          glyphs((row * glyphColumns + col) * GlyphInfo.glyphHeight + i) = lineInt.U(8.W)
+        }
+      }
+    }
+    val currentDir = System.getProperty("user.dir")
+    val hexTxtPath = Paths.get(currentDir, "verilog", f"${fontBitmapFilename}.txt")
+    val writer = new FileWriter(hexTxtPath.toString)
+    for (i <- glyphs.indices) {
+      writer.write(f"@$i%x\n${glyphs(i).litValue}%02x\n")
+    }
+    writer.close()
+    (hexTxtPath, glyphs.length)
+  }
+}

lab3/src/main/scala/peripheral/HDMIDisplay.scala

@@ -0,0 +1,403 @@
+// Copyright 2022 hrpccs
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package peripheral
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+class HDMISync extends Module {
+  val io = IO(new Bundle {
+    val hsync = Output(Bool())
+    val vsync = Output(Bool())
+    val video_on = Output(Bool())
+    val p_tick = Output(Bool())
+    val f_tick = Output(Bool())
+    val x = Output(UInt(10.W))
+    val y = Output(UInt(10.W))
+  })
+
+  val DisplayHorizontal = ScreenInfo.DisplayHorizontal
+  val DisplayVertical = ScreenInfo.DisplayVertical
+
+  val BorderLeft = 48
+  val BorderRight = 16
+  val BorderTop = 10
+  val BorderBottom = 33
+
+  val RetraceHorizontal = 96
+  val RetraceVertical = 2
+
+  val MaxHorizontal = DisplayHorizontal + BorderLeft + BorderRight + RetraceHorizontal - 1
+  val MaxVertical = DisplayVertical + BorderTop + BorderBottom + RetraceVertical - 1
+
+  val RetraceHorizontalStart = DisplayHorizontal + BorderRight
+  val RetraceHorizontalEnd = RetraceHorizontalStart + RetraceHorizontal - 1
+
+  val RetraceVerticalStart = DisplayVertical + BorderBottom
+  val RetraceVerticalEnd = RetraceVerticalStart + RetraceVertical - 1
+
+  val pixel = RegInit(UInt(3.W), 0.U)
+  val pixel_next = Wire(UInt(3.W))
+  val pixel_tick = Wire(Bool())
+
+  val v_count_reg = RegInit(UInt(10.W), 0.U)
+  val h_count_reg = RegInit(UInt(10.W), 0.U)
+
+  val v_count_next = Wire(UInt(10.W))
+  val h_count_next = Wire(UInt(10.W))
+
+  val vsync_reg = RegInit(Bool(), false.B)
+  val hsync_reg = RegInit(Bool(), false.B)
+
+  val vsync_next = Wire(Bool())
+  val hsync_next = Wire(Bool())
+
+  pixel_next := Mux(pixel === 4.U, 0.U, pixel + 1.U)
+  pixel_tick := pixel === 0.U
+
+  h_count_next := Mux(
+    pixel_tick,
+    Mux(h_count_reg === MaxHorizontal.U, 0.U, h_count_reg + 1.U),
+    h_count_reg
+  )
+
+  v_count_next := Mux(
+    pixel_tick && h_count_reg === MaxHorizontal.U,
+    Mux(v_count_reg === MaxVertical.U, 0.U, v_count_reg + 1.U),
+    v_count_reg
+  )
+
+  hsync_next := h_count_reg >= RetraceHorizontalStart.U && h_count_reg <= RetraceHorizontalEnd.U
+  vsync_next := v_count_reg >= RetraceVerticalStart.U && v_count_reg <= RetraceVerticalEnd.U
+
+  pixel := pixel_next
+  hsync_reg := hsync_next
+  vsync_reg := vsync_next
+  v_count_reg := v_count_next
+  h_count_reg := h_count_next
+
+  io.video_on := h_count_reg < DisplayHorizontal.U && v_count_reg < DisplayVertical.U
+  io.hsync := hsync_reg
+  io.vsync := vsync_reg
+  io.x := h_count_reg
+  io.y := v_count_reg
+  io.p_tick := pixel_tick
+  io.f_tick := io.x === 0.U && io.y === 0.U
+}
+
+class TMDS_encoder extends Module {
+  val io = IO(new Bundle() {
+    val video_data = Input(UInt(8.W)) //r,g,b,8bit
+    val control_data = Input(UInt(2.W))
+    val video_on = Input(Bool())
+    val TMDS = Output(UInt(10.W))
+  })
+  val Nb1s = PopCount(io.video_data)
+  val XNOR = Wire(Bool())
+  XNOR := (Nb1s > 4.U(4.W)) || (Nb1s === 4.U(4.W) && io.video_data(0) === 0.U)
+  val xored = 1.U(1.W) ## xorfunc(io.video_data)
+  val xnored = 0.U(1.W) ## xnorfunc(io.video_data)
+  val q_m = Mux(
+    XNOR,
+    xnored,
+    xored
+  )
+  val diff = PopCount(q_m).asSInt - 4.S
+  val diffSize = diff.getWidth
+  val disparitySize = 4
+  val disparityReg = RegInit(0.S(disparitySize.W))
+  val doutReg = RegInit("b1010101011".U(10.W))
+
+  //using recursion to compute
+  def xorfunc(value: UInt): UInt = {
+    value.getWidth match {
+      case 1 => value(0)
+      case s => val res = xorfunc(VecInit(value.asBools.drop(1)).asUInt)
+        value.asBools.head ^ res.asBools.head ## res
+    }
+  }
+
+  def xnorfunc(value: UInt): UInt = {
+    value.getWidth match {
+      case 1 => value(0)
+      case s => val res = xnorfunc(VecInit(value.asBools.drop(1)).asUInt)
+        !(value.asBools.head ^ res.asBools.head) ## res
+    }
+  }
+
+  when(io.video_on === false.B) {
+    disparityReg := 0.S
+    doutReg := "b1010101011".U(10.W)
+    switch(io.control_data) {
+      is("b00".U(2.W)) {
+        doutReg := "b1101010100".U(10.W)
+      }
+      is("b01".U(2.W)) {
+        doutReg := "b0010101011".U(10.W)
+      }
+      is("b10".U(2.W)) {
+        doutReg := "b0101010100".U(10.W)
+      }
+    }
+  }.otherwise {
+    when(disparityReg === 0.S || diff === 0.S) {
+      when(q_m(8) === false.B) {
+        doutReg := "b10".U(2.W) ## q_m(7, 0)
+        disparityReg := disparityReg - diff
+      }.otherwise {
+        doutReg := "b01".U(2.W) ## q_m(7, 0)
+        disparityReg := disparityReg + diff
+      }
+    }.elsewhen((!diff(diffSize - 1) && !disparityReg(disparitySize - 1))
+      || (diff(diffSize - 1) && disparityReg(disparitySize - 1))) {
+      doutReg := 1.U(1.W) ## q_m(8) ## ~q_m(7, 0)
+      when(q_m(8)) {
+        disparityReg := disparityReg + 1.S - diff
+      }.otherwise {
+        disparityReg := disparityReg - diff
+      }
+    }.otherwise {
+      doutReg := 0.U(1.W) ## q_m
+      when(q_m(8)) {
+        disparityReg := disparityReg + diff
+      }.otherwise {
+        disparityReg := disparityReg - 1.S + diff
+      }
+    }
+  }
+
+  io.TMDS := doutReg
+}
+
+class HDMIDisplay extends Module {
+  val io = IO(new Bundle() {
+    val bundle = new RAMBundle
+
+    val TMDSclk_p = Output(Bool())
+    val TMDSdata_p = Output(UInt(3.W))
+    val TMDSclk_n = Output(Bool())
+    val TMDSdata_n = Output(UInt(3.W))
+  })
+
+  val mem = Module(new BlockRAM(ScreenInfo.Chars / Parameters.WordSize))
+  mem.io.write_enable := io.bundle.write_enable
+  mem.io.write_data := io.bundle.write_data
+  mem.io.write_address := io.bundle.address
+  mem.io.write_strobe := io.bundle.write_strobe
+
+  mem.io.read_address := io.bundle.address
+  io.bundle.read_data := mem.io.read_data
+
+  val pixel_clk = Wire(Bool())
+  val hsync = Wire(Bool())
+  val vsync = Wire(Bool())
+  val sync = Module(new HDMISync)
+  hsync := sync.io.hsync
+  vsync := sync.io.vsync
+  pixel_clk := sync.io.p_tick
+
+  val font_rom = Module(new FontROM)
+  val row = (sync.io.y >> log2Up(GlyphInfo.glyphHeight)).asUInt
+  val col = (sync.io.x >> log2Up(GlyphInfo.glyphWidth)).asUInt
+  val char_index = (row * ScreenInfo.CharCols.U) + col
+  val offset = char_index(1, 0)
+  val ch = Wire(UInt(8.W))
+
+  mem.io.debug_read_address := char_index
+  ch := MuxLookup(
+    offset,
+    0.U,
+    IndexedSeq(
+      0.U -> mem.io.debug_read_data(7, 0).asUInt,
+      1.U -> mem.io.debug_read_data(15, 8).asUInt,
+      2.U -> mem.io.debug_read_data(23, 16).asUInt,
+      3.U -> mem.io.debug_read_data(31, 24).asUInt
+    )
+  )
+  font_rom.io.glyph_index := Mux(ch >= 32.U, ch - 31.U, 0.U)
+  font_rom.io.glyph_y := sync.io.y(log2Up(GlyphInfo.glyphHeight) - 1, 0)
+  val rgb = Wire(UInt(24.W)) //RGB 8:8:8
+  // White if pixel_on and glyph pixel on
+  val glyph_x = sync.io.x(log2Up(GlyphInfo.glyphWidth) - 1, 0)
+  rgb := Mux(sync.io.video_on && font_rom.io.glyph_pixel_byte(glyph_x), 0xFFFFFFF.U, 0.U)
+  //TMDS_PLLVR is a vivado IP core, check it in /verilog/pynq/TMDS_PLLVR.v
+  val serial_clk = Wire(Clock())
+  val pll_lock = Wire(Bool())
+  val tmdspll = Module(new TMDS_PLLVR)
+  val rst = Wire(Reset())
+  tmdspll.io.clkin := pixel_clk.asClock
+  serial_clk := tmdspll.io.clkout
+  pll_lock := tmdspll.io.lock
+  tmdspll.io.reset := reset
+  rst := ~pll_lock
+
+  val tmds = Wire(UInt(3.W))
+  val tmds_clk = Wire(Bool())
+  withClockAndReset(pixel_clk.asClock, rst) {
+    val tmds_channel1 = Wire(UInt(10.W))
+    val tmds_channel2 = Wire(UInt(10.W))
+    val tmds_channel0 = Wire(UInt(10.W))
+
+    val tmds_green = Module(new TMDS_encoder)
+    val tmds_red = Module(new TMDS_encoder)
+    val tmds_blue = Module(new TMDS_encoder)
+
+    tmds_red.io.video_on := sync.io.video_on
+    tmds_blue.io.video_on := sync.io.video_on
+    tmds_green.io.video_on := sync.io.video_on
+
+    tmds_blue.io.control_data := sync.io.vsync ## sync.io.hsync
+    tmds_green.io.control_data := 0.U
+    tmds_red.io.control_data := 0.U
+
+    tmds_red.io.video_data := rgb(23, 16)
+    tmds_blue.io.video_data := rgb(15, 8)
+    tmds_green.io.video_data := rgb(7, 0)
+
+    tmds_channel0 := tmds_blue.io.TMDS
+    tmds_channel1 := tmds_green.io.TMDS
+    tmds_channel2 := tmds_red.io.TMDS
+
+    val serdesBlue = Module(new Oser10Module())
+    serdesBlue.io.data := tmds_channel0
+    serdesBlue.io.fclk := serial_clk
+
+    val serdesGreen = Module(new Oser10Module())
+    serdesGreen.io.data := tmds_channel1
+    serdesGreen.io.fclk := serial_clk
+
+    val serdesRed = Module(new Oser10Module())
+    serdesRed.io.data := tmds_channel2
+    serdesRed.io.fclk := serial_clk
+
+    tmds := serdesRed.io.q ## serdesGreen.io.q ## serdesBlue.io.q
+
+    //serdesCLk : 25Mhz ,Why not directly use p_tick?
+    //cause Duty Ratio of p_tick is 10% , while which of serdesCLk is 50%
+    val serdesClk = Module(new Oser10Module())
+    serdesClk.io.data := "b1111100000".U(10.W)
+    serdesClk.io.fclk := serial_clk
+
+    tmds_clk := serdesClk.io.q
+
+    val buffDiffBlue = Module(new OBUFDS)
+    buffDiffBlue.io.I := tmds(0)
+    val buffDiffGreen = Module(new OBUFDS)
+    buffDiffGreen.io.I := tmds(1)
+    val buffDiffRed = Module(new OBUFDS)
+    buffDiffRed.io.I := tmds(2)
+    val buffDiffClk = Module(new OBUFDS)
+    buffDiffClk.io.I := tmds_clk
+
+    io.TMDSclk_p := buffDiffClk.io.O
+    io.TMDSclk_n := buffDiffClk.io.OB
+    io.TMDSdata_p := buffDiffRed.io.O ## buffDiffGreen.io.O ## buffDiffBlue.io.O
+    io.TMDSdata_n := buffDiffRed.io.OB ## buffDiffGreen.io.OB ## buffDiffBlue.io.OB
+  }
+}
+
+//----------------------------------------
+//PLL frequency multiplier using BlackBox
+class TMDS_PLLVR extends BlackBox {
+  val io = IO(new Bundle {
+    val clkin = Input(Clock())
+    val reset = Input(Reset())
+    val clkout = Output(Clock())
+    val clkoutd = Output(Clock())
+    val lock = Output(Bool())
+  })
+}
+
+/* OSER10 : serializer 10:1*/
+class OSER10 extends Module {
+  val io = IO(new Bundle {
+    val Q = Output(Bool()) // OSER10 data output signal
+    val D0 = Input(Bool())
+    val D1 = Input(Bool())
+    val D2 = Input(Bool())
+    val D3 = Input(Bool())
+    val D4 = Input(Bool())
+    val D5 = Input(Bool())
+    val D6 = Input(Bool())
+    val D7 = Input(Bool())
+    val D8 = Input(Bool())
+    val D9 = Input(Bool()) //  OSER10 data input signal
+    val PCLK = Input(Clock()) // Primary clock input signal
+    val FCLK = Input(Clock()) // High speed clock input signal
+    val RESET = Input(Reset()) // Asynchronous reset input signal,
+    //active-high.
+  })
+  withClockAndReset(io.FCLK, io.RESET) {
+    val count = RegInit(0.U(4.W))
+    val countnext = Wire(UInt(4.W))
+    io.Q := MuxLookup(
+      count,
+      0.U,
+      IndexedSeq(
+        0.U -> io.D0.asBool,
+        1.U -> io.D1.asBool,
+        2.U -> io.D2.asBool,
+        3.U -> io.D3.asBool,
+        4.U -> io.D4.asBool,
+        5.U -> io.D5.asBool,
+        6.U -> io.D6.asBool,
+        7.U -> io.D7.asBool,
+        8.U -> io.D8.asBool,
+        9.U -> io.D9.asBool
+      )
+    )
+    countnext := Mux(
+      count === 9.U, 0.U, count + 1.U
+    )
+    count := countnext
+  }
+}
+
+class Oser10Module extends Module {
+  val io = IO(new Bundle {
+    val q = Output(Bool())
+    val data = Input(UInt(10.W))
+    val fclk = Input(Clock()) // Fast clock
+  })
+
+  val osr10 = Module(new OSER10())
+  io.q := osr10.io.Q
+  osr10.io.D0 := io.data(0)
+  osr10.io.D1 := io.data(1)
+  osr10.io.D2 := io.data(2)
+  osr10.io.D3 := io.data(3)
+  osr10.io.D4 := io.data(4)
+  osr10.io.D5 := io.data(5)
+  osr10.io.D6 := io.data(6)
+  osr10.io.D7 := io.data(7)
+  osr10.io.D8 := io.data(8)
+  osr10.io.D9 := io.data(9)
+  osr10.io.PCLK := clock
+  osr10.io.FCLK := io.fclk
+  osr10.io.RESET := reset
+}
+
+/* lvds output */
+class OBUFDS extends BlackBox {
+  val io = IO(new Bundle {
+    val O = Output(Bool())
+    val OB = Output(Bool())
+    val I = Input(Bool())
+  })
+}
+//-----------------------------------------
+
+

lab3/src/main/scala/peripheral/InstructionROM.scala

@@ -0,0 +1,68 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package peripheral
+
+import chisel3._
+import chisel3.experimental.{ChiselAnnotation, annotate}
+import chisel3.util.experimental.loadMemoryFromFileInline
+import firrtl.annotations.MemorySynthInit
+import riscv.Parameters
+
+import java.io.FileWriter
+import java.nio.file.{Files, Paths}
+import java.nio.{ByteBuffer, ByteOrder}
+
+class InstructionROM(instructionFilename: String) extends Module {
+  val io = IO(new Bundle {
+    val address = Input(UInt(Parameters.AddrWidth))
+    val data = Output(UInt(Parameters.InstructionWidth))
+  })
+
+  val (instructionsInitFile, capacity) = readAsmBinary(instructionFilename)
+  val mem = Mem(capacity, UInt(Parameters.InstructionWidth))
+  annotate(new ChiselAnnotation {
+    override def toFirrtl =
+      MemorySynthInit
+  })
+  loadMemoryFromFileInline(mem, instructionsInitFile.toString.replaceAll("\\\\", "/"))
+  io.data := mem.read(io.address)
+
+  def readAsmBinary(filename: String) = {
+    val inputStream = if (Files.exists(Paths.get(filename))) {
+      Files.newInputStream(Paths.get(filename))
+    } else {
+      getClass.getClassLoader.getResourceAsStream(filename)
+    }
+    var instructions = new Array[BigInt](0)
+    val arr = new Array[Byte](4)
+    while (inputStream.read(arr) == 4) {
+      val instBuf = ByteBuffer.wrap(arr)
+      instBuf.order(ByteOrder.LITTLE_ENDIAN)
+      val inst = BigInt(instBuf.getInt() & 0xFFFFFFFFL)
+      instructions = instructions :+ inst
+    }
+    instructions = instructions :+ BigInt(0x00000013L)
+    instructions = instructions :+ BigInt(0x00000013L)
+    instructions = instructions :+ BigInt(0x00000013L)
+    val currentDir = System.getProperty("user.dir")
+    val exeTxtPath = Paths.get(currentDir, "verilog", f"${instructionFilename}.txt")
+    val writer = new FileWriter(exeTxtPath.toString)
+    for (i <- instructions.indices) {
+      writer.write(f"@$i%x\n${instructions(i)}%08x\n")
+    }
+    writer.close()
+    (exeTxtPath, instructions.length)
+  }
+}

lab3/src/main/scala/peripheral/Memory.scala

@@ -0,0 +1,77 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package peripheral
+
+import chisel3._
+import riscv.Parameters
+
+class RAMBundle extends Bundle {
+  val address = Input(UInt(Parameters.AddrWidth))
+  val write_data = Input(UInt(Parameters.DataWidth))
+  val write_enable = Input(Bool())
+  val write_strobe = Input(Vec(Parameters.WordSize, Bool()))
+  val read_data = Output(UInt(Parameters.DataWidth))
+}
+
+// The purpose of this module is to help the synthesis tool recognize
+// our memory as a Block RAM template
+class BlockRAM(capacity: Int) extends Module {
+  val io = IO(new Bundle {
+    val read_address = Input(UInt(Parameters.AddrWidth))
+    val write_address = Input(UInt(Parameters.AddrWidth))
+    val write_data = Input(UInt(Parameters.DataWidth))
+    val write_enable = Input(Bool())
+    val write_strobe = Input(Vec(Parameters.WordSize, Bool()))
+
+    val debug_read_address = Input(UInt(Parameters.AddrWidth))
+
+    val read_data = Output(UInt(Parameters.DataWidth))
+    val debug_read_data = Output(UInt(Parameters.DataWidth))
+  })
+  val mem = SyncReadMem(capacity, Vec(Parameters.WordSize, UInt(Parameters.ByteWidth)))
+  when(io.write_enable) {
+    val write_data_vec = Wire(Vec(Parameters.WordSize, UInt(Parameters.ByteWidth)))
+    for (i <- 0 until Parameters.WordSize) {
+      write_data_vec(i) := io.write_data((i + 1) * Parameters.ByteBits - 1, i * Parameters.ByteBits)
+    }
+    mem.write((io.write_address >> 2.U).asUInt, write_data_vec, io.write_strobe)
+  }
+  io.read_data := mem.read((io.read_address >> 2.U).asUInt, true.B).asUInt
+  io.debug_read_data := mem.read((io.debug_read_address >> 2.U).asUInt, true.B).asUInt
+}
+
+class Memory(capacity: Int) extends Module {
+  val io = IO(new Bundle {
+    val bundle = new RAMBundle
+
+    val instruction = Output(UInt(Parameters.DataWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+
+    val debug_read_address = Input(UInt(Parameters.AddrWidth))
+    val debug_read_data = Output(UInt(Parameters.DataWidth))
+  })
+
+  val mem = SyncReadMem(capacity, Vec(Parameters.WordSize, UInt(Parameters.ByteWidth)))
+  when(io.bundle.write_enable) {
+    val write_data_vec = Wire(Vec(Parameters.WordSize, UInt(Parameters.ByteWidth)))
+    for (i <- 0 until Parameters.WordSize) {
+      write_data_vec(i) := io.bundle.write_data((i + 1) * Parameters.ByteBits - 1, i * Parameters.ByteBits)
+    }
+    mem.write((io.bundle.address >> 2.U).asUInt, write_data_vec, io.bundle.write_strobe)
+  }
+  io.bundle.read_data := mem.read((io.bundle.address >> 2.U).asUInt, true.B).asUInt
+  io.debug_read_data := mem.read((io.debug_read_address >> 2.U).asUInt, true.B).asUInt
+  io.instruction := mem.read((io.instruction_address >> 2.U).asUInt, true.B).asUInt
+}

lab3/src/main/scala/peripheral/ROMLoader.scala

@@ -0,0 +1,50 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package peripheral
+
+import chisel3._
+import riscv.Parameters
+
+class ROMLoader(capacity: Int) extends Module {
+  val io = IO(new Bundle {
+    val bundle = Flipped(new RAMBundle)
+
+    val rom_address = Output(UInt(Parameters.AddrWidth))
+    val rom_data = Input(UInt(Parameters.InstructionWidth))
+
+    val load_address = Input(UInt(Parameters.AddrWidth))
+    val load_finished = Output(Bool())
+  })
+
+  val address = RegInit(0.U(32.W))
+  val valid = RegInit(false.B)
+
+  io.bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(false.B))
+  io.bundle.address := 0.U
+  io.bundle.write_data := 0.U
+  io.bundle.write_enable := false.B
+  when(address <= (capacity - 1).U) {
+    io.bundle.write_enable := true.B
+    io.bundle.write_data := io.rom_data
+    io.bundle.address := (address << 2.U).asUInt + io.load_address
+    io.bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(true.B))
+    address := address + 1.U
+    when(address === (capacity - 1).U) {
+      valid := true.B
+    }
+  }
+  io.load_finished := valid
+  io.rom_address := address
+}

lab3/src/main/scala/peripheral/Timer.scala

@@ -0,0 +1,60 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package peripheral
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+class Timer extends Module {
+  val io = IO(new Bundle {
+    val bundle = new RAMBundle
+    val signal_interrupt = Output(Bool())
+
+    val debug_limit = Output(UInt(Parameters.DataWidth))
+    val debug_enabled = Output(Bool())
+  })
+
+  val count = RegInit(0.U(32.W))
+  val limit = RegInit(100000000.U(32.W))
+  io.debug_limit := limit
+  val enabled = RegInit(true.B)
+  io.debug_enabled := enabled
+
+  io.bundle.read_data := MuxLookup(
+    io.bundle.address,
+    0.U,
+    IndexedSeq(
+      0x4.U -> limit,
+      0x8.U -> enabled.asUInt,
+    )
+  )
+  when(io.bundle.write_enable) {
+    when(io.bundle.address === 0x4.U) {
+      limit := io.bundle.write_data
+      count := 0.U
+    }.elsewhen(io.bundle.address === 0x8.U) {
+      enabled := io.bundle.write_data =/= 0.U
+    }
+  }
+
+  io.signal_interrupt := enabled && (count >= (limit - 10.U))
+
+  when(count >= limit) {
+    count := 0.U
+  }.otherwise {
+    count := count + 1.U
+  }
+}

lab3/src/main/scala/peripheral/UART.scala

@@ -0,0 +1,204 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package peripheral
+
+import chisel3._
+import chisel3.util._
+
+class UartIO extends DecoupledIO(UInt(8.W)) {
+}
+
+
+/**
+ * Transmit part of the UART.
+ * A minimal version without any additional buffering.
+ * Use a ready/valid handshaking.
+ */
+class Tx(frequency: Int, baudRate: Int) extends Module {
+  val io = IO(new Bundle {
+    val txd = Output(UInt(1.W))
+    val channel = Flipped(new UartIO())
+
+  })
+
+  val BIT_CNT = ((frequency + baudRate / 2) / baudRate - 1).U
+
+  val shiftReg = RegInit(0x7ff.U)
+  val cntReg = RegInit(0.U(20.W))
+  val bitsReg = RegInit(0.U(4.W))
+
+  io.channel.ready := (cntReg === 0.U) && (bitsReg === 0.U)
+  io.txd := shiftReg(0)
+
+  when(cntReg === 0.U) {
+
+    cntReg := BIT_CNT
+    when(bitsReg =/= 0.U) {
+      val shift = shiftReg >> 1
+      shiftReg := Cat(1.U, shift(9, 0))
+      bitsReg := bitsReg - 1.U
+    }.otherwise {
+      when(io.channel.valid) {
+        shiftReg := Cat(Cat(3.U, io.channel.bits), 0.U) // two stop bits, data, one start bit
+        bitsReg := 11.U
+      }.otherwise {
+        shiftReg := 0x7ff.U
+      }
+    }
+
+  }.otherwise {
+    cntReg := cntReg - 1.U
+  }
+}
+
+/**
+ * Receive part of the UART.
+ * A minimal version without any additional buffering.
+ * Use a ready/valid handshaking.
+ *
+ * The following code is inspired by Tommy's receive code at:
+ * https://github.com/tommythorn/yarvi
+ */
+class Rx(frequency: Int, baudRate: Int) extends Module {
+  val io = IO(new Bundle {
+    val rxd = Input(UInt(1.W))
+    val channel = new UartIO()
+
+  })
+
+  val BIT_CNT = ((frequency + baudRate / 2) / baudRate - 1).U
+  val START_CNT = ((3 * frequency / 2 + baudRate / 2) / baudRate - 1).U
+
+  // Sync in the asynchronous RX data, reset to 1 to not start reading after a reset
+  val rxReg = RegNext(RegNext(io.rxd, 1.U), 1.U)
+
+  val shiftReg = RegInit(0.U(8.W))
+  val cntReg = RegInit(0.U(20.W))
+  val bitsReg = RegInit(0.U(4.W))
+  val valReg = RegInit(false.B)
+
+  when(cntReg =/= 0.U) {
+    cntReg := cntReg - 1.U
+  }.elsewhen(bitsReg =/= 0.U) {
+    cntReg := BIT_CNT
+    shiftReg := Cat(rxReg, shiftReg >> 1)
+    bitsReg := bitsReg - 1.U
+    // the last shifted in
+    when(bitsReg === 1.U) {
+      valReg := true.B
+    }
+  }.elsewhen(rxReg === 0.U) { // wait 1.5 bits after falling edge of start
+    cntReg := START_CNT
+    bitsReg := 8.U
+  }
+
+  when(valReg && io.channel.ready) {
+    valReg := false.B
+  }
+
+  io.channel.bits := shiftReg
+  io.channel.valid := valReg
+}
+
+/**
+ * A single byte buffer with a ready/valid interface
+ */
+class Buffer extends Module {
+  val io = IO(new Bundle {
+    val in = Flipped(new UartIO())
+    val out = new UartIO()
+  })
+
+  val empty :: full :: Nil = Enum(2)
+  val stateReg = RegInit(empty)
+  val dataReg = RegInit(0.U(8.W))
+
+  io.in.ready := stateReg === empty
+  io.out.valid := stateReg === full
+
+  when(stateReg === empty) {
+    when(io.in.valid) {
+      dataReg := io.in.bits
+      stateReg := full
+    }
+  }.otherwise { // full
+    when(io.out.ready) {
+      stateReg := empty
+    }
+  }
+  io.out.bits := dataReg
+}
+
+/**
+ * A transmitter with a single buffer.
+ */
+class BufferedTx(frequency: Int, baudRate: Int) extends Module {
+  val io = IO(new Bundle {
+    val txd = Output(UInt(1.W))
+    val channel = Flipped(new UartIO())
+
+  })
+  val tx = Module(new Tx(frequency, baudRate))
+  val buf = Module(new Buffer)
+
+  buf.io.in <> io.channel
+  tx.io.channel <> buf.io.out
+  io.txd <> tx.io.txd
+}
+
+class Uart(frequency: Int, baudRate: Int) extends Module {
+  val io = IO(new Bundle {
+    val bundle = new RAMBundle
+    val rxd = Input(UInt(1.W))
+    val txd = Output(UInt(1.W))
+
+    val signal_interrupt = Output(Bool())
+  })
+  val interrupt = RegInit(false.B)
+  val rxData = RegInit(0.U)
+
+  val tx = Module(new BufferedTx(frequency, baudRate))
+  val rx = Module(new Rx(frequency, baudRate))
+
+  io.bundle.read_data := 0.U
+  when(io.bundle.address === 0x4.U) {
+    io.bundle.read_data := baudRate.U
+  }.elsewhen(io.bundle.address === 0xC.U) {
+    io.bundle.read_data := rxData
+    interrupt := false.B
+  }
+
+  tx.io.channel.valid := false.B
+  tx.io.channel.bits := 0.U
+  when(io.bundle.write_enable) {
+    when(io.bundle.address === 0x8.U) {
+      interrupt := io.bundle.write_data =/= 0.U
+    }.elsewhen(io.bundle.address === 0x10.U) {
+      tx.io.channel.valid := true.B
+      tx.io.channel.bits := io.bundle.write_data
+    }
+  }
+
+  io.txd := tx.io.txd
+  rx.io.rxd := io.rxd
+
+  io.signal_interrupt := interrupt
+  rx.io.channel.ready := false.B
+  when(rx.io.channel.valid) {
+    rx.io.channel.ready := true.B
+    rxData := rx.io.channel.bits
+    interrupt := true.B
+  }
+}

lab3/src/main/scala/peripheral/VGADisplay.scala

@@ -0,0 +1,164 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package peripheral
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+object GlyphInfo {
+  val glyphWidth = 8
+  val glyphHeight = 16
+  // ASCII printable characters start from here
+  val spaceIndex = 1
+}
+
+object ScreenInfo {
+  val DisplayHorizontal = 640
+  val DisplayVertical = 480
+
+  val CharCols = DisplayHorizontal / GlyphInfo.glyphWidth
+  val CharRows = DisplayVertical / GlyphInfo.glyphHeight
+  val Chars = CharCols * CharRows
+}
+
+
+class VGASync extends Module {
+  val io = IO(new Bundle {
+    val hsync = Output(Bool())
+    val vsync = Output(Bool())
+    val video_on = Output(Bool())
+    val p_tick = Output(Bool())
+    val f_tick = Output(Bool())
+    val x = Output(UInt(10.W))
+    val y = Output(UInt(10.W))
+  })
+
+  val DisplayHorizontal = ScreenInfo.DisplayHorizontal
+  val DisplayVertical = ScreenInfo.DisplayVertical
+
+  val BorderLeft = 48
+  val BorderRight = 16
+  val BorderTop = 10
+  val BorderBottom = 33
+
+  val RetraceHorizontal = 96
+  val RetraceVertical = 2
+
+  val MaxHorizontal = DisplayHorizontal + BorderLeft + BorderRight + RetraceHorizontal - 1
+  val MaxVertical = DisplayVertical + BorderTop + BorderBottom + RetraceVertical - 1
+
+  val RetraceHorizontalStart = DisplayHorizontal + BorderRight
+  val RetraceHorizontalEnd = RetraceHorizontalStart + RetraceHorizontal - 1
+
+  val RetraceVerticalStart = DisplayVertical + BorderBottom
+  val RetraceVerticalEnd = RetraceVerticalStart + RetraceVertical - 1
+
+  val pixel = RegInit(UInt(2.W), 0.U)
+  val pixel_next = Wire(UInt(2.W))
+  val pixel_tick = Wire(Bool())
+
+  val v_count_reg = RegInit(UInt(10.W), 0.U)
+  val h_count_reg = RegInit(UInt(10.W), 0.U)
+
+  val v_count_next = Wire(UInt(10.W))
+  val h_count_next = Wire(UInt(10.W))
+
+  val vsync_reg = RegInit(Bool(), false.B)
+  val hsync_reg = RegInit(Bool(), false.B)
+
+  val vsync_next = Wire(Bool())
+  val hsync_next = Wire(Bool())
+
+  pixel_next := pixel + 1.U
+  pixel_tick := pixel === 0.U
+
+  h_count_next := Mux(
+    pixel_tick,
+    Mux(h_count_reg === MaxHorizontal.U, 0.U, h_count_reg + 1.U),
+    h_count_reg
+  )
+
+  v_count_next := Mux(
+    pixel_tick && h_count_reg === MaxHorizontal.U,
+    Mux(v_count_reg === MaxVertical.U, 0.U, v_count_reg + 1.U),
+    v_count_reg
+  )
+
+  hsync_next := h_count_reg >= RetraceHorizontalStart.U && h_count_reg <= RetraceHorizontalEnd.U
+  vsync_next := v_count_reg >= RetraceVerticalStart.U && v_count_reg <= RetraceVerticalEnd.U
+
+  pixel := pixel_next
+  hsync_reg := hsync_next
+  vsync_reg := vsync_next
+  v_count_reg := v_count_next
+  h_count_reg := h_count_next
+
+  io.video_on := h_count_reg < DisplayHorizontal.U && v_count_reg < DisplayVertical.U
+  io.hsync := hsync_reg
+  io.vsync := vsync_reg
+  io.x := h_count_reg
+  io.y := v_count_reg
+  io.p_tick := pixel_tick
+  io.f_tick := io.x === 0.U && io.y === 0.U
+}
+
+class VGADisplay extends Module {
+  val io = IO(new Bundle() {
+    val bundle = new RAMBundle
+
+    val hsync = Output(Bool())
+    val vsync = Output(Bool())
+
+    val rgb = Output(UInt(12.W))
+  })
+  val mem = Module(new BlockRAM(ScreenInfo.Chars / Parameters.WordSize))
+  mem.io.write_enable := io.bundle.write_enable
+  mem.io.write_data := io.bundle.write_data
+  mem.io.write_address := io.bundle.write_data
+  mem.io.write_strobe := io.bundle.write_strobe
+
+  mem.io.read_address := io.bundle.address
+  io.bundle.read_data := mem.io.read_data
+
+  val sync = Module(new VGASync)
+  io.hsync := sync.io.hsync
+  io.vsync := sync.io.vsync
+
+  val font_rom = Module(new FontROM)
+  val row = (sync.io.y >> log2Up(GlyphInfo.glyphHeight)).asUInt
+  val col = (sync.io.x >> log2Up(GlyphInfo.glyphWidth)).asUInt
+  val char_index = (row * ScreenInfo.CharCols.U) + col
+  val offset = char_index(1, 0)
+  val ch = Wire(UInt(8.W))
+
+  mem.io.debug_read_address := char_index
+  ch := MuxLookup(
+    offset,
+    0.U,
+    IndexedSeq(
+      0.U -> mem.io.debug_read_data(7, 0).asUInt,
+      1.U -> mem.io.debug_read_data(15, 8).asUInt,
+      2.U -> mem.io.debug_read_data(23, 16).asUInt,
+      3.U -> mem.io.debug_read_data(31, 24).asUInt
+    )
+  )
+  font_rom.io.glyph_index := Mux(ch >= 32.U, ch - 31.U, 0.U)
+  font_rom.io.glyph_y := sync.io.y(log2Up(GlyphInfo.glyphHeight) - 1, 0)
+
+  // White if pixel_on and glyph pixel on
+  val glyph_x = sync.io.x(log2Up(GlyphInfo.glyphWidth) - 1, 0)
+  io.rgb := Mux(sync.io.video_on && font_rom.io.glyph_pixel_byte(glyph_x), 0xFFFF.U, 0.U)
+}

lab3/src/main/scala/riscv/Parameters.scala

@@ -0,0 +1,60 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv
+
+import chisel3._
+import chisel3.util._
+
+object ImplementationType {
+  val ThreeStage = 0
+  val FiveStageStall = 1
+  val FiveStageForward = 2
+  val FiveStageFinal = 3
+}
+
+object Parameters {
+  val AddrBits = 32
+  val AddrWidth = AddrBits.W
+
+  val InstructionBits = 32
+  val InstructionWidth = InstructionBits.W
+  val DataBits = 32
+  val DataWidth = DataBits.W
+  val ByteBits = 8
+  val ByteWidth = ByteBits.W
+  val WordSize = Math.ceil(DataBits / ByteBits).toInt
+
+  val PhysicalRegisters = 32
+  val PhysicalRegisterAddrBits = log2Up(PhysicalRegisters)
+  val PhysicalRegisterAddrWidth = PhysicalRegisterAddrBits.W
+
+  val CSRRegisterAddrBits = 12
+  val CSRRegisterAddrWidth = CSRRegisterAddrBits.W
+
+  val InterruptFlagBits = 32
+  val InterruptFlagWidth = InterruptFlagBits.W
+
+  val HoldStateBits = 3
+  val StallStateWidth = HoldStateBits.W
+
+  val MemorySizeInBytes = 32768
+  val MemorySizeInWords = MemorySizeInBytes / 4
+
+  val EntryAddress = 0x1000.U(Parameters.AddrWidth)
+
+  val MasterDeviceCount = 1
+  val SlaveDeviceCount = 8
+  val SlaveDeviceCountBits = log2Up(Parameters.SlaveDeviceCount)
+}

lab3/src/main/scala/riscv/core/ALU.scala

@@ -0,0 +1,69 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core
+
+import chisel3._
+import chisel3.experimental.ChiselEnum
+import chisel3.util._
+import riscv.Parameters
+
+object ALUFunctions extends ChiselEnum {
+  val zero, add, sub, sll, slt, xor, or, and, srl, sra, sltu = Value
+}
+
+class ALU extends Module {
+  val io = IO(new Bundle {
+    val func = Input(ALUFunctions())
+
+    val op1 = Input(UInt(Parameters.DataWidth))
+    val op2 = Input(UInt(Parameters.DataWidth))
+
+    val result = Output(UInt(Parameters.DataWidth))
+  })
+
+  io.result := 0.U
+  switch(io.func) {
+    is(ALUFunctions.add) {
+      io.result := io.op1 + io.op2
+    }
+    is(ALUFunctions.sub) {
+      io.result := io.op1 - io.op2
+    }
+    is(ALUFunctions.sll) {
+      io.result := io.op1 << io.op2(4, 0)
+    }
+    is(ALUFunctions.slt) {
+      io.result := io.op1.asSInt < io.op2.asSInt
+    }
+    is(ALUFunctions.xor) {
+      io.result := io.op1 ^ io.op2
+    }
+    is(ALUFunctions.or) {
+      io.result := io.op1 | io.op2
+    }
+    is(ALUFunctions.and) {
+      io.result := io.op1 & io.op2
+    }
+    is(ALUFunctions.srl) {
+      io.result := io.op1 >> io.op2(4, 0)
+    }
+    is(ALUFunctions.sra) {
+      io.result := (io.op1.asSInt >> io.op2(4, 0)).asUInt
+    }
+    is(ALUFunctions.sltu) {
+      io.result := io.op1 < io.op2
+    }
+  }
+}

lab3/src/main/scala/riscv/core/ALUControl.scala

@@ -0,0 +1,87 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core
+
+import chisel3._
+import chisel3.util._
+import riscv.core.threestage.{InstructionTypes, Instructions, InstructionsTypeI, InstructionsTypeR}
+
+class ALUControl extends Module {
+  val io = IO(new Bundle {
+    val opcode = Input(UInt(7.W))
+    val funct3 = Input(UInt(3.W))
+    val funct7 = Input(UInt(7.W))
+
+    val alu_funct = Output(ALUFunctions())
+  })
+
+  io.alu_funct := ALUFunctions.zero
+
+  switch(io.opcode) {
+    is(InstructionTypes.I) {
+      io.alu_funct := MuxLookup(
+        io.funct3,
+        ALUFunctions.zero,
+        IndexedSeq(
+          InstructionsTypeI.addi -> ALUFunctions.add,
+          InstructionsTypeI.slli -> ALUFunctions.sll,
+          InstructionsTypeI.slti -> ALUFunctions.slt,
+          InstructionsTypeI.sltiu -> ALUFunctions.sltu,
+          InstructionsTypeI.xori -> ALUFunctions.xor,
+          InstructionsTypeI.ori -> ALUFunctions.or,
+          InstructionsTypeI.andi -> ALUFunctions.and,
+          InstructionsTypeI.sri -> Mux(io.funct7(5), ALUFunctions.sra, ALUFunctions.srl)
+        ),
+      )
+    }
+    is(InstructionTypes.RM) {
+      io.alu_funct := MuxLookup(
+        io.funct3,
+        ALUFunctions.zero,
+        IndexedSeq(
+          InstructionsTypeR.add_sub -> Mux(io.funct7(5), ALUFunctions.sub, ALUFunctions.add),
+          InstructionsTypeR.sll -> ALUFunctions.sll,
+          InstructionsTypeR.slt -> ALUFunctions.slt,
+          InstructionsTypeR.sltu -> ALUFunctions.sltu,
+          InstructionsTypeR.xor -> ALUFunctions.xor,
+          InstructionsTypeR.or -> ALUFunctions.or,
+          InstructionsTypeR.and -> ALUFunctions.and,
+          InstructionsTypeR.sr -> Mux(io.funct7(5), ALUFunctions.sra, ALUFunctions.srl)
+        ),
+      )
+    }
+    is(InstructionTypes.B) {
+      io.alu_funct := ALUFunctions.add
+    }
+    is(InstructionTypes.L) {
+      io.alu_funct := ALUFunctions.add
+    }
+    is(InstructionTypes.S) {
+      io.alu_funct := ALUFunctions.add
+    }
+    is(Instructions.jal) {
+      io.alu_funct := ALUFunctions.add
+    }
+    is(Instructions.jalr) {
+      io.alu_funct := ALUFunctions.add
+    }
+    is(Instructions.lui) {
+      io.alu_funct := ALUFunctions.add
+    }
+    is(Instructions.auipc) {
+      io.alu_funct := ALUFunctions.add
+    }
+  }
+}

lab3/src/main/scala/riscv/core/CPU.scala

@@ -0,0 +1,40 @@
+// Copyright 2022 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core
+
+import chisel3._
+import riscv.ImplementationType
+import riscv.core.fivestage_final.{CPU => FiveStageCPUFinal}
+import riscv.core.fivestage_forward.{CPU => FiveStageCPUForward}
+import riscv.core.fivestage_stall.{CPU => FiveStageCPUStall}
+import riscv.core.threestage.{CPU => ThreeStageCPU}
+
+class CPU(val implementation: Int = ImplementationType.FiveStageFinal) extends Module {
+  val io = IO(new CPUBundle)
+  implementation match {
+    case ImplementationType.ThreeStage =>
+      val cpu = Module(new ThreeStageCPU)
+      cpu.io <> io
+    case ImplementationType.FiveStageStall =>
+      val cpu = Module(new FiveStageCPUStall)
+      cpu.io <> io
+    case ImplementationType.FiveStageForward =>
+      val cpu = Module(new FiveStageCPUForward)
+      cpu.io <> io
+    case _ =>
+      val cpu = Module(new FiveStageCPUFinal)
+      cpu.io <> io
+  }
+}

lab3/src/main/scala/riscv/core/CPUBundle.scala

@@ -0,0 +1,30 @@
+// Copyright 2022 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core
+
+import chisel3._
+import peripheral.RAMBundle
+import riscv.Parameters
+
+class CPUBundle extends Bundle {
+  val instruction_address = Output(UInt(Parameters.AddrWidth))
+  val instruction = Input(UInt(Parameters.DataWidth))
+  val instruction_valid = Input(Bool())
+  val memory_bundle = Flipped(new RAMBundle)
+  val device_select = Output(UInt(Parameters.SlaveDeviceCountBits.W))
+  val interrupt_flag = Input(UInt(Parameters.InterruptFlagWidth))
+  val debug_read_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+  val debug_read_data = Output(UInt(Parameters.DataWidth))
+}

lab3/src/main/scala/riscv/core/CSR.scala

@@ -0,0 +1,99 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+import riscv.core.threestage.CSRDirectAccessBundle
+
+
+object CSRRegister {
+  // Refer to Spec. Vol.II Page 8-10
+  val MSTATUS = 0x300.U(Parameters.CSRRegisterAddrWidth)
+  val MIE = 0x304.U(Parameters.CSRRegisterAddrWidth)
+  val MTVEC = 0x305.U(Parameters.CSRRegisterAddrWidth)
+  val MSCRATCH = 0x340.U(Parameters.CSRRegisterAddrWidth)
+  val MEPC = 0x341.U(Parameters.CSRRegisterAddrWidth)
+  val MCAUSE = 0x342.U(Parameters.CSRRegisterAddrWidth)
+  val CycleL = 0xc00.U(Parameters.CSRRegisterAddrWidth)
+  val CycleH = 0xc80.U(Parameters.CSRRegisterAddrWidth)
+}
+
+class CSR extends Module {
+  val io = IO(new Bundle {
+    val reg_read_address_id = Input(UInt(Parameters.CSRRegisterAddrWidth))
+    val reg_write_enable_ex = Input(Bool())
+    val reg_write_address_ex = Input(UInt(Parameters.CSRRegisterAddrWidth))
+    val reg_write_data_ex = Input(UInt(Parameters.DataWidth))
+
+    val id_reg_read_data = Output(UInt(Parameters.DataWidth))
+
+    val clint_access_bundle = Flipped(new CSRDirectAccessBundle)
+  })
+
+  val mstatus = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val mie = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val mtvec = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val mscratch = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val mepc = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val mcause = RegInit(UInt(Parameters.DataWidth), 0.U)
+  val cycles = RegInit(UInt(64.W), 0.U)
+  val regLUT =
+    IndexedSeq(
+      CSRRegister.MSTATUS -> mstatus,
+      CSRRegister.MIE -> mie,
+      CSRRegister.MTVEC -> mtvec,
+      CSRRegister.MSCRATCH -> mscratch,
+      CSRRegister.MEPC -> mepc,
+      CSRRegister.MCAUSE -> mcause,
+      CSRRegister.CycleL -> cycles(31, 0),
+      CSRRegister.CycleH -> cycles(63, 32),
+    )
+  cycles := cycles + 1.U
+
+  // If the pipeline and the CLINT are going to read and write the CSR at the same time, let the pipeline write first.
+  // This is implemented in a single cycle by passing reg_write_data_ex to clint and writing the data from the CLINT to the CSR.
+  io.id_reg_read_data := MuxLookup(io.reg_read_address_id, 0.U, regLUT)
+
+  io.clint_access_bundle.mstatus := Mux(io.reg_write_enable_ex && io.reg_write_address_ex === CSRRegister.MSTATUS, io.reg_write_data_ex, mstatus)
+  io.clint_access_bundle.mtvec := Mux(io.reg_write_enable_ex && io.reg_write_address_ex === CSRRegister.MTVEC, io.reg_write_data_ex, mtvec)
+  io.clint_access_bundle.mcause := Mux(io.reg_write_enable_ex && io.reg_write_address_ex === CSRRegister.MCAUSE, io.reg_write_data_ex, mcause)
+  io.clint_access_bundle.mepc := Mux(io.reg_write_enable_ex && io.reg_write_address_ex === CSRRegister.MEPC, io.reg_write_data_ex, mepc)
+
+  when(io.clint_access_bundle.direct_write_enable) {
+    mstatus := io.clint_access_bundle.mstatus_write_data
+    mepc := io.clint_access_bundle.mepc_write_data
+    mcause := io.clint_access_bundle.mcause_write_data
+  }.elsewhen(io.reg_write_enable_ex) {
+    when(io.reg_write_address_ex === CSRRegister.MSTATUS) {
+      mstatus := io.reg_write_data_ex
+    }.elsewhen(io.reg_write_address_ex === CSRRegister.MEPC) {
+      mepc := io.reg_write_data_ex
+    }.elsewhen(io.reg_write_address_ex === CSRRegister.MCAUSE) {
+      mcause := io.reg_write_data_ex
+    }
+  }
+
+  when(io.reg_write_enable_ex) {
+    when(io.reg_write_address_ex === CSRRegister.MIE) {
+      mie := io.reg_write_data_ex
+    }.elsewhen(io.reg_write_address_ex === CSRRegister.MTVEC) {
+      mtvec := io.reg_write_data_ex
+    }.elsewhen(io.reg_write_address_ex === CSRRegister.MSCRATCH) {
+      mscratch := io.reg_write_data_ex
+    }
+  }
+}

lab3/src/main/scala/riscv/core/PipelineRegister.scala

@@ -0,0 +1,30 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core
+
+import chisel3._
+import riscv.Parameters
+
+class PipelineRegister(width: Int = Parameters.DataBits, defaultValue: UInt = 0.U) extends Module {
+  val io = IO(new Bundle {
+    val stall = Input(Bool())
+    val flush = Input(Bool())
+    val in = Input(UInt(width.W))
+    val out = Output(UInt(width.W))
+  })
+  // Lab3(PipelineRegister)
+  io.out := 0.U
+  // Lab3(PipelineRegister) End
+}

lab3/src/main/scala/riscv/core/RegisterFile.scala

@@ -0,0 +1,78 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+object Registers extends Enumeration {
+  type Register = Value
+  val zero,
+  ra, sp, gp, tp,
+  t0, t1, t2, fp,
+  s1,
+  a0, a1, a2, a3, a4, a5, a6, a7,
+  s2, s3, s4, s5, s6, s7, s8, s9, s10, s11,
+  t3, t4, t5, t6 = Value
+}
+
+class RegisterFile extends Module {
+  val io = IO(new Bundle {
+    val write_enable = Input(Bool())
+    val write_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val write_data = Input(UInt(Parameters.DataWidth))
+
+    val read_address1 = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val read_address2 = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val read_data1 = Output(UInt(Parameters.DataWidth))
+    val read_data2 = Output(UInt(Parameters.DataWidth))
+
+    val debug_read_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val debug_read_data = Output(UInt(Parameters.DataWidth))
+  })
+  val registers = Reg(Vec(Parameters.PhysicalRegisters, UInt(Parameters.DataWidth)))
+
+  when(!reset.asBool) {
+    when(io.write_enable && io.write_address =/= 0.U) {
+      registers(io.write_address) := io.write_data
+    }
+  }
+
+  io.read_data1 := MuxCase(
+    registers(io.read_address1),
+    IndexedSeq(
+      (io.read_address1 === 0.U) -> 0.U,
+      (io.read_address1 === io.write_address && io.write_enable) -> io.write_data
+    )
+  )
+
+  io.read_data2 := MuxCase(
+    registers(io.read_address2),
+    IndexedSeq(
+      (io.read_address2 === 0.U) -> 0.U,
+      (io.read_address2 === io.write_address && io.write_enable) -> io.write_data
+    )
+  )
+
+  io.debug_read_data := MuxCase(
+    registers(io.debug_read_address),
+    IndexedSeq(
+      (io.debug_read_address === 0.U) -> 0.U,
+      (io.debug_read_address === io.write_address && io.write_enable) -> io.write_data
+    )
+  )
+
+}

lab3/src/main/scala/riscv/core/fivestage_final/CLINT.scala

@@ -0,0 +1,101 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import chisel3.util.MuxLookup
+import riscv.Parameters
+
+object InterruptStatus {
+  val None = 0x0.U(8.W)
+  val Timer0 = 0x1.U(8.W)
+  val Ret = 0xFF.U(8.W)
+}
+
+class CSRDirectAccessBundle extends Bundle {
+  val mstatus = Input(UInt(Parameters.DataWidth))
+  val mepc = Input(UInt(Parameters.DataWidth))
+  val mcause = Input(UInt(Parameters.DataWidth))
+  val mtvec = Input(UInt(Parameters.DataWidth))
+
+  val mstatus_write_data = Output(UInt(Parameters.DataWidth))
+  val mepc_write_data = Output(UInt(Parameters.DataWidth))
+  val mcause_write_data = Output(UInt(Parameters.DataWidth))
+
+  val direct_write_enable = Output(Bool())
+}
+
+// Core Local Interrupt Controller
+class CLINT extends Module {
+  val io = IO(new Bundle {
+    val interrupt_flag = Input(UInt(Parameters.InterruptFlagWidth))
+
+    val instruction_id = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address_if = Input(UInt(Parameters.AddrWidth))
+
+    val jump_flag = Input(Bool())
+    val jump_address = Input(UInt(Parameters.AddrWidth))
+
+    val id_interrupt_handler_address = Output(UInt(Parameters.AddrWidth))
+    val id_interrupt_assert = Output(Bool())
+
+    val csr_bundle = new CSRDirectAccessBundle
+  })
+  val interrupt_enable = io.csr_bundle.mstatus(3)
+  val instruction_address = Mux(
+    io.jump_flag,
+    io.jump_address,
+    io.instruction_address_if,
+  )
+  val mstatus_disable_interrupt = io.csr_bundle.mstatus(31, 4) ## 0.U(1.W) ## io.csr_bundle.mstatus(2, 0)
+  val mstatus_recover_interrupt = io.csr_bundle.mstatus(31, 4) ## io.csr_bundle.mstatus(7) ## io.csr_bundle.mstatus(2, 0)
+
+  when(io.instruction_id === InstructionsEnv.ecall || io.instruction_id === InstructionsEnv.ebreak) {
+    io.csr_bundle.mstatus_write_data := mstatus_disable_interrupt
+    io.csr_bundle.mepc_write_data := instruction_address
+    io.csr_bundle.mcause_write_data := MuxLookup(
+      io.instruction_id,
+      10.U,
+      IndexedSeq(
+        InstructionsEnv.ecall -> 11.U,
+        InstructionsEnv.ebreak -> 3.U,
+      )
+    )
+    io.csr_bundle.direct_write_enable := true.B
+    io.id_interrupt_assert := true.B
+    io.id_interrupt_handler_address := io.csr_bundle.mtvec
+  }.elsewhen(io.interrupt_flag =/= InterruptStatus.None && interrupt_enable) {
+    io.csr_bundle.mstatus_write_data := mstatus_disable_interrupt
+    io.csr_bundle.mepc_write_data := instruction_address
+    io.csr_bundle.mcause_write_data := Mux(io.interrupt_flag(0), 0x80000007L.U, 0x8000000BL.U)
+    io.csr_bundle.direct_write_enable := true.B
+    io.id_interrupt_assert := true.B
+    io.id_interrupt_handler_address := io.csr_bundle.mtvec
+  }.elsewhen(io.instruction_id === InstructionsRet.mret) {
+    io.csr_bundle.mstatus_write_data := mstatus_recover_interrupt
+    io.csr_bundle.mepc_write_data := io.csr_bundle.mepc
+    io.csr_bundle.mcause_write_data := io.csr_bundle.mcause
+    io.csr_bundle.direct_write_enable := true.B
+    io.id_interrupt_assert := true.B
+    io.id_interrupt_handler_address := io.csr_bundle.mepc
+  }.otherwise {
+    io.csr_bundle.mstatus_write_data := io.csr_bundle.mstatus
+    io.csr_bundle.mepc_write_data := io.csr_bundle.mepc
+    io.csr_bundle.mcause_write_data := io.csr_bundle.mcause
+    io.csr_bundle.direct_write_enable := false.B
+    io.id_interrupt_assert := false.B
+    io.id_interrupt_handler_address := 0.U
+  }
+}

lab3/src/main/scala/riscv/core/fivestage_final/CPU.scala

@@ -0,0 +1,169 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.{CPUBundle, CSR, RegisterFile}
+
+class CPU extends Module {
+  val io = IO(new CPUBundle)
+
+  val ctrl = Module(new Control)
+  val regs = Module(new RegisterFile)
+  val inst_fetch = Module(new InstructionFetch)
+  val if2id = Module(new IF2ID)
+  val id = Module(new InstructionDecode)
+  val id2ex = Module(new ID2EX)
+  val ex = Module(new Execute)
+  val ex2mem = Module(new EX2MEM)
+  val mem = Module(new MemoryAccess)
+  val mem2wb = Module(new MEM2WB)
+  val wb = Module(new WriteBack)
+  val forwarding = Module(new Forwarding)
+  val clint = Module(new CLINT)
+  val csr_regs = Module(new CSR)
+
+  ctrl.io.jump_flag := id.io.if_jump_flag
+  ctrl.io.jump_instruction_id := id.io.ctrl_jump_instruction
+  ctrl.io.rs1_id := id.io.regs_reg1_read_address
+  ctrl.io.rs2_id := id.io.regs_reg2_read_address
+  ctrl.io.memory_read_enable_ex := id2ex.io.output_memory_read_enable
+  ctrl.io.rd_ex := id2ex.io.output_regs_write_address
+  ctrl.io.memory_read_enable_mem := ex2mem.io.output_memory_read_enable
+  ctrl.io.rd_mem := ex2mem.io.output_regs_write_address
+
+  regs.io.write_enable := mem2wb.io.output_regs_write_enable
+  regs.io.write_address := mem2wb.io.output_regs_write_address
+  regs.io.write_data := wb.io.regs_write_data
+  regs.io.read_address1 := id.io.regs_reg1_read_address
+  regs.io.read_address2 := id.io.regs_reg2_read_address
+
+  regs.io.debug_read_address := io.debug_read_address
+  io.debug_read_data := regs.io.debug_read_data
+
+  io.instruction_address := inst_fetch.io.instruction_address
+  inst_fetch.io.stall_flag_ctrl := ctrl.io.pc_stall
+  inst_fetch.io.jump_flag_id := id.io.if_jump_flag
+  inst_fetch.io.jump_address_id := id.io.if_jump_address
+  inst_fetch.io.rom_instruction := io.instruction
+  inst_fetch.io.instruction_valid := io.instruction_valid
+
+  if2id.io.stall := ctrl.io.if_stall
+  if2id.io.flush := ctrl.io.if_flush
+  if2id.io.instruction := inst_fetch.io.id_instruction
+  if2id.io.instruction_address := inst_fetch.io.instruction_address
+  if2id.io.interrupt_flag := io.interrupt_flag
+
+  id.io.instruction := if2id.io.output_instruction
+  id.io.instruction_address := if2id.io.output_instruction_address
+  id.io.reg1_data := regs.io.read_data1
+  id.io.reg2_data := regs.io.read_data2
+  id.io.forward_from_mem := mem.io.forward_data
+  id.io.forward_from_wb := wb.io.regs_write_data
+  id.io.reg1_forward := forwarding.io.reg1_forward_id
+  id.io.reg2_forward := forwarding.io.reg2_forward_id
+  id.io.interrupt_assert := clint.io.id_interrupt_assert
+  id.io.interrupt_handler_address := clint.io.id_interrupt_handler_address
+
+  id2ex.io.flush := ctrl.io.id_flush
+  id2ex.io.instruction := if2id.io.output_instruction
+  id2ex.io.instruction_address := if2id.io.output_instruction_address
+  id2ex.io.reg1_data := regs.io.read_data1
+  id2ex.io.reg2_data := regs.io.read_data2
+  id2ex.io.regs_reg1_read_address := id.io.regs_reg1_read_address
+  id2ex.io.regs_reg2_read_address := id.io.regs_reg2_read_address
+  id2ex.io.regs_write_enable := id.io.ex_reg_write_enable
+  id2ex.io.regs_write_address := id.io.ex_reg_write_address
+  id2ex.io.regs_write_source := id.io.ex_reg_write_source
+  id2ex.io.immediate := id.io.ex_immediate
+  id2ex.io.aluop1_source := id.io.ex_aluop1_source
+  id2ex.io.aluop2_source := id.io.ex_aluop2_source
+  id2ex.io.csr_write_enable := id.io.ex_csr_write_enable
+  id2ex.io.csr_address := id.io.ex_csr_address
+  id2ex.io.memory_read_enable := id.io.ex_memory_read_enable
+  id2ex.io.memory_write_enable := id.io.ex_memory_write_enable
+  id2ex.io.csr_read_data := csr_regs.io.id_reg_read_data
+
+  ex.io.instruction := id2ex.io.output_instruction
+  ex.io.instruction_address := id2ex.io.output_instruction_address
+  ex.io.reg1_data := id2ex.io.output_reg1_data
+  ex.io.reg2_data := id2ex.io.output_reg2_data
+  ex.io.immediate := id2ex.io.output_immediate
+  ex.io.aluop1_source := id2ex.io.output_aluop1_source
+  ex.io.aluop2_source := id2ex.io.output_aluop2_source
+  ex.io.csr_read_data := id2ex.io.output_csr_read_data
+  ex.io.forward_from_mem := mem.io.forward_data
+  ex.io.forward_from_wb := wb.io.regs_write_data
+  ex.io.reg1_forward := forwarding.io.reg1_forward_ex
+  ex.io.reg2_forward := forwarding.io.reg2_forward_ex
+
+  ex2mem.io.regs_write_enable := id2ex.io.output_regs_write_enable
+  ex2mem.io.regs_write_source := id2ex.io.output_regs_write_source
+  ex2mem.io.regs_write_address := id2ex.io.output_regs_write_address
+  ex2mem.io.instruction_address := id2ex.io.output_instruction_address
+  ex2mem.io.funct3 := id2ex.io.output_instruction(14, 12)
+  ex2mem.io.reg2_data := ex.io.mem_reg2_data
+  ex2mem.io.memory_read_enable := id2ex.io.output_memory_read_enable
+  ex2mem.io.memory_write_enable := id2ex.io.output_memory_write_enable
+  ex2mem.io.alu_result := ex.io.mem_alu_result
+  ex2mem.io.csr_read_data := id2ex.io.output_csr_read_data
+
+  mem.io.alu_result := ex2mem.io.output_alu_result
+  mem.io.reg2_data := ex2mem.io.output_reg2_data
+  mem.io.memory_read_enable := ex2mem.io.output_memory_read_enable
+  mem.io.memory_write_enable := ex2mem.io.output_memory_write_enable
+  mem.io.funct3 := ex2mem.io.output_funct3
+  mem.io.regs_write_source := ex2mem.io.output_regs_write_source
+  mem.io.csr_read_data := ex2mem.io.output_csr_read_data
+  io.device_select := mem.io.bundle.address(Parameters.AddrBits - 1, Parameters.AddrBits - Parameters.SlaveDeviceCountBits)
+  io.memory_bundle <> mem.io.bundle
+  io.memory_bundle.address := 0.U(Parameters.SlaveDeviceCountBits.W) ## mem.io.bundle.address(Parameters.AddrBits - 1 - Parameters.SlaveDeviceCountBits, 0)
+
+  mem2wb.io.instruction_address := ex2mem.io.output_instruction_address
+  mem2wb.io.alu_result := ex2mem.io.output_alu_result
+  mem2wb.io.regs_write_enable := ex2mem.io.output_regs_write_enable
+  mem2wb.io.regs_write_source := ex2mem.io.output_regs_write_source
+  mem2wb.io.regs_write_address := ex2mem.io.output_regs_write_address
+  mem2wb.io.memory_read_data := mem.io.wb_memory_read_data
+  mem2wb.io.csr_read_data := ex2mem.io.output_csr_read_data
+
+  wb.io.instruction_address := mem2wb.io.output_instruction_address
+  wb.io.alu_result := mem2wb.io.output_alu_result
+  wb.io.memory_read_data := mem2wb.io.output_memory_read_data
+  wb.io.regs_write_source := mem2wb.io.output_regs_write_source
+  wb.io.csr_read_data := mem2wb.io.output_csr_read_data
+
+  forwarding.io.rs1_id := id.io.regs_reg1_read_address
+  forwarding.io.rs2_id := id.io.regs_reg2_read_address
+  forwarding.io.rs1_ex := id2ex.io.output_regs_reg1_read_address
+  forwarding.io.rs2_ex := id2ex.io.output_regs_reg2_read_address
+  forwarding.io.rd_mem := ex2mem.io.output_regs_write_address
+  forwarding.io.reg_write_enable_mem := ex2mem.io.output_regs_write_enable
+  forwarding.io.rd_wb := mem2wb.io.output_regs_write_address
+  forwarding.io.reg_write_enable_wb := mem2wb.io.output_regs_write_enable
+
+  clint.io.instruction_address_if := inst_fetch.io.instruction_address
+  clint.io.instruction_id := if2id.io.output_instruction
+  clint.io.jump_flag := id.io.clint_jump_flag
+  clint.io.jump_address := id.io.clint_jump_address
+  clint.io.interrupt_flag := if2id.io.output_interrupt_flag
+  clint.io.csr_bundle <> csr_regs.io.clint_access_bundle
+
+  csr_regs.io.reg_read_address_id := id.io.ex_csr_address
+  csr_regs.io.reg_write_enable_ex := id2ex.io.output_csr_write_enable
+  csr_regs.io.reg_write_address_ex := id2ex.io.output_csr_address
+  csr_regs.io.reg_write_data_ex := ex.io.csr_write_data
+}

lab3/src/main/scala/riscv/core/fivestage_final/Control.scala

@@ -0,0 +1,43 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import riscv.Parameters
+
+class Control extends Module {
+  val io = IO(new Bundle {
+    val jump_flag = Input(Bool())
+    val jump_instruction_id = Input(Bool())
+    val rs1_id = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val rs2_id = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val memory_read_enable_ex = Input(Bool())
+    val rd_ex = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val memory_read_enable_mem = Input(Bool())
+    val rd_mem = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+
+    val if_flush = Output(Bool())
+    val id_flush = Output(Bool())
+    val pc_stall = Output(Bool())
+    val if_stall = Output(Bool())
+  })
+
+  // Lab3(Final)
+  io.if_flush := false.B
+  io.id_flush := false.B
+  io.pc_stall := false.B
+  io.if_stall := false.B
+  // Lab3(Final) End
+}

lab3/src/main/scala/riscv/core/fivestage_final/EX2MEM.scala

@@ -0,0 +1,108 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class EX2MEM extends Module {
+  val io = IO(new Bundle() {
+    val regs_write_enable = Input(Bool())
+    val regs_write_source = Input(UInt(2.W))
+    val regs_write_address = Input(UInt(Parameters.AddrWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val funct3 = Input(UInt(3.W))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val memory_read_enable = Input(Bool())
+    val memory_write_enable = Input(Bool())
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val output_regs_write_enable = Output(Bool())
+    val output_regs_write_source = Output(UInt(2.W))
+    val output_regs_write_address = Output(UInt(Parameters.AddrWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_funct3 = Output(UInt(Parameters.DataWidth))
+    val output_reg2_data = Output(UInt(Parameters.DataWidth))
+    val output_memory_read_enable = Output(Bool())
+    val output_memory_write_enable = Output(Bool())
+    val output_alu_result = Output(UInt(Parameters.DataWidth))
+    val output_csr_read_data = Output(UInt(Parameters.DataWidth))
+  })
+
+  val stall = false.B
+  val flush = false.B
+
+  val regs_write_enable = Module(new PipelineRegister(1))
+  regs_write_enable.io.in := io.regs_write_enable
+  regs_write_enable.io.stall := stall
+  regs_write_enable.io.flush := flush
+  io.output_regs_write_enable := regs_write_enable.io.out
+
+  val regs_write_source = Module(new PipelineRegister(2))
+  regs_write_source.io.in := io.regs_write_source
+  regs_write_source.io.stall := stall
+  regs_write_source.io.flush := flush
+  io.output_regs_write_source := regs_write_source.io.out
+
+  val regs_write_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_write_address.io.in := io.regs_write_address
+  regs_write_address.io.stall := stall
+  regs_write_address.io.flush := flush
+  io.output_regs_write_address := regs_write_address.io.out
+
+  val instruction_address = Module(new PipelineRegister(Parameters.AddrBits))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val funct3 = Module(new PipelineRegister(3))
+  funct3.io.in := io.funct3
+  funct3.io.stall := stall
+  funct3.io.flush := flush
+  io.output_funct3 := funct3.io.out
+
+  val reg2_data = Module(new PipelineRegister())
+  reg2_data.io.in := io.reg2_data
+  reg2_data.io.stall := stall
+  reg2_data.io.flush := flush
+  io.output_reg2_data := reg2_data.io.out
+
+  val alu_result = Module(new PipelineRegister())
+  alu_result.io.in := io.alu_result
+  alu_result.io.stall := stall
+  alu_result.io.flush := flush
+  io.output_alu_result := alu_result.io.out
+
+  val memory_read_enable = Module(new PipelineRegister(1))
+  memory_read_enable.io.in := io.memory_read_enable
+  memory_read_enable.io.stall := stall
+  memory_read_enable.io.flush := flush
+  io.output_memory_read_enable := memory_read_enable.io.out
+
+  val memory_write_enable = Module(new PipelineRegister(1))
+  memory_write_enable.io.in := io.memory_write_enable
+  memory_write_enable.io.stall := stall
+  memory_write_enable.io.flush := flush
+  io.output_memory_write_enable := memory_write_enable.io.out
+
+  val csr_read_data = Module(new PipelineRegister())
+  csr_read_data.io.in := io.csr_read_data
+  csr_read_data.io.stall := stall
+  csr_read_data.io.flush := flush
+  io.output_csr_read_data := csr_read_data.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_final/Execute.scala

@@ -0,0 +1,93 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+import riscv.core.{ALU, ALUControl}
+
+
+class Execute extends Module {
+  val io = IO(new Bundle {
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val reg1_data = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val immediate = Input(UInt(Parameters.DataWidth))
+    val aluop1_source = Input(UInt(1.W))
+    val aluop2_source = Input(UInt(1.W))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+    val forward_from_mem = Input(UInt(Parameters.DataWidth))
+    val forward_from_wb = Input(UInt(Parameters.DataWidth))
+    val reg1_forward = Input(UInt(2.W))
+    val reg2_forward = Input(UInt(2.W))
+
+    val mem_alu_result = Output(UInt(Parameters.DataWidth))
+    val mem_reg2_data = Output(UInt(Parameters.DataWidth))
+    val csr_write_data = Output(UInt(Parameters.DataWidth))
+  })
+
+  val opcode = io.instruction(6, 0)
+  val funct3 = io.instruction(14, 12)
+  val funct7 = io.instruction(31, 25)
+  val uimm = io.instruction(19, 15)
+
+  val alu = Module(new ALU)
+  val alu_ctrl = Module(new ALUControl)
+
+  alu_ctrl.io.opcode := opcode
+  alu_ctrl.io.funct3 := funct3
+  alu_ctrl.io.funct7 := funct7
+  alu.io.func := alu_ctrl.io.alu_funct
+
+  val reg1_data = MuxLookup(
+    io.reg1_forward,
+    io.reg1_data,
+    IndexedSeq(
+      ForwardingType.ForwardFromMEM -> io.forward_from_mem,
+      ForwardingType.ForwardFromWB -> io.forward_from_wb
+    )
+  )
+  alu.io.op1 := Mux(
+    io.aluop1_source === ALUOp1Source.InstructionAddress,
+    io.instruction_address,
+    reg1_data
+  )
+
+  val reg2_data = MuxLookup(
+    io.reg2_forward,
+    io.reg2_data,
+    IndexedSeq(
+      ForwardingType.ForwardFromMEM -> io.forward_from_mem,
+      ForwardingType.ForwardFromWB -> io.forward_from_wb
+    )
+  )
+  alu.io.op2 := Mux(
+    io.aluop2_source === ALUOp2Source.Immediate,
+    io.immediate,
+    reg2_data
+  )
+  io.mem_alu_result := alu.io.result
+  io.mem_reg2_data := reg2_data
+  io.csr_write_data := MuxLookup(funct3, 0.U, IndexedSeq(
+    InstructionsTypeCSR.csrrw -> reg1_data,
+    InstructionsTypeCSR.csrrc -> io.csr_read_data.&((~reg1_data).asUInt),
+    InstructionsTypeCSR.csrrs -> io.csr_read_data.|(reg1_data),
+    InstructionsTypeCSR.csrrwi -> Cat(0.U(27.W), uimm),
+    InstructionsTypeCSR.csrrci -> io.csr_read_data.&((~Cat(0.U(27.W), uimm)).asUInt),
+    InstructionsTypeCSR.csrrsi -> io.csr_read_data.|(Cat(0.U(27.W), uimm)),
+  ))
+}

lab3/src/main/scala/riscv/core/fivestage_final/Forwarding.scala

@@ -0,0 +1,49 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import riscv.Parameters
+
+object ForwardingType {
+  val NoForward = 0.U(2.W)
+  val ForwardFromMEM = 1.U(2.W)
+  val ForwardFromWB = 2.U(2.W)
+}
+
+class Forwarding extends Module {
+  val io = IO(new Bundle() {
+    val rs1_id = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val rs2_id = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val rs1_ex = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val rs2_ex = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val rd_mem = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val reg_write_enable_mem = Input(Bool())
+    val rd_wb = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val reg_write_enable_wb = Input(Bool())
+
+    val reg1_forward_id = Output(UInt(2.W))
+    val reg2_forward_id = Output(UInt(2.W))
+    val reg1_forward_ex = Output(UInt(2.W))
+    val reg2_forward_ex = Output(UInt(2.W))
+  })
+
+  // Lab3(Final)
+  io.reg1_forward_id := 0.U
+  io.reg2_forward_id := 0.U
+  io.reg1_forward_ex := 0.U
+  io.reg2_forward_ex := 0.U
+  // Lab3(Final) End
+}

lab3/src/main/scala/riscv/core/fivestage_final/ID2EX.scala

@@ -0,0 +1,163 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class ID2EX extends Module {
+  val io = IO(new Bundle {
+    val flush = Input(Bool())
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val regs_reg1_read_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_reg2_read_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_write_enable = Input(Bool())
+    val regs_write_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_write_source = Input(UInt(2.W))
+    val reg1_data = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val immediate = Input(UInt(Parameters.DataWidth))
+    val aluop1_source = Input(UInt(1.W))
+    val aluop2_source = Input(UInt(1.W))
+    val csr_write_enable = Input(Bool())
+    val csr_address = Input(UInt(Parameters.CSRRegisterAddrWidth))
+    val memory_read_enable = Input(Bool())
+    val memory_write_enable = Input(Bool())
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val output_instruction = Output(UInt(Parameters.DataWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_regs_reg1_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val output_regs_reg2_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val output_regs_write_enable = Output(Bool())
+    val output_regs_write_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val output_regs_write_source = Output(UInt(2.W))
+    val output_reg1_data = Output(UInt(Parameters.DataWidth))
+    val output_reg2_data = Output(UInt(Parameters.DataWidth))
+    val output_immediate = Output(UInt(Parameters.DataWidth))
+    val output_aluop1_source = Output(UInt(1.W))
+    val output_aluop2_source = Output(UInt(1.W))
+    val output_csr_write_enable = Output(Bool())
+    val output_csr_address = Output(UInt(Parameters.CSRRegisterAddrWidth))
+    val output_memory_read_enable = Output(Bool())
+    val output_memory_write_enable = Output(Bool())
+    val output_csr_read_data = Output(UInt(Parameters.DataWidth))
+  })
+  val stall = false.B
+
+  val instruction = Module(new PipelineRegister(defaultValue = InstructionsNop.nop))
+  instruction.io.in := io.instruction
+  instruction.io.stall := stall
+  instruction.io.flush := io.flush
+  io.output_instruction := instruction.io.out
+
+  val instruction_address = Module(new PipelineRegister(defaultValue = ProgramCounter.EntryAddress))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := io.flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val regs_reg1_read_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_reg1_read_address.io.in := io.regs_reg1_read_address
+  regs_reg1_read_address.io.stall := stall
+  regs_reg1_read_address.io.flush := io.flush
+  io.output_regs_reg1_read_address := regs_reg1_read_address.io.out
+
+  val regs_reg2_read_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_reg2_read_address.io.in := io.regs_reg2_read_address
+  regs_reg2_read_address.io.stall := stall
+  regs_reg2_read_address.io.flush := io.flush
+  io.output_regs_reg2_read_address := regs_reg2_read_address.io.out
+
+  val regs_write_enable = Module(new PipelineRegister(1))
+  regs_write_enable.io.in := io.regs_write_enable
+  regs_write_enable.io.stall := stall
+  regs_write_enable.io.flush := io.flush
+  io.output_regs_write_enable := regs_write_enable.io.out
+
+  val regs_write_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_write_address.io.in := io.regs_write_address
+  regs_write_address.io.stall := stall
+  regs_write_address.io.flush := io.flush
+  io.output_regs_write_address := regs_write_address.io.out
+
+  val regs_write_source = Module(new PipelineRegister(2))
+  regs_write_source.io.in := io.regs_write_source
+  regs_write_source.io.stall := stall
+  regs_write_source.io.flush := io.flush
+  io.output_regs_write_source := regs_write_source.io.out
+
+  val reg1_data = Module(new PipelineRegister())
+  reg1_data.io.in := io.reg1_data
+  reg1_data.io.stall := stall
+  reg1_data.io.flush := io.flush
+  io.output_reg1_data := reg1_data.io.out
+
+  val reg2_data = Module(new PipelineRegister())
+  reg2_data.io.in := io.reg2_data
+  reg2_data.io.stall := stall
+  reg2_data.io.flush := io.flush
+  io.output_reg2_data := reg2_data.io.out
+
+  val immediate = Module(new PipelineRegister())
+  immediate.io.in := io.immediate
+  immediate.io.stall := stall
+  immediate.io.flush := io.flush
+  io.output_immediate := immediate.io.out
+
+  val aluop1_source = Module(new PipelineRegister(1))
+  aluop1_source.io.in := io.aluop1_source
+  aluop1_source.io.stall := stall
+  aluop1_source.io.flush := io.flush
+  io.output_aluop1_source := aluop1_source.io.out
+
+  val aluop2_source = Module(new PipelineRegister(1))
+  aluop2_source.io.in := io.aluop2_source
+  aluop2_source.io.stall := stall
+  aluop2_source.io.flush := io.flush
+  io.output_aluop2_source := aluop2_source.io.out
+
+  val csr_write_enable = Module(new PipelineRegister(1))
+  csr_write_enable.io.in := io.csr_write_enable
+  csr_write_enable.io.stall := stall
+  csr_write_enable.io.flush := io.flush
+  io.output_csr_write_enable := csr_write_enable.io.out
+
+  val csr_address = Module(new PipelineRegister(Parameters.CSRRegisterAddrBits))
+  csr_address.io.in := io.csr_address
+  csr_address.io.stall := stall
+  csr_address.io.flush := io.flush
+  io.output_csr_address := csr_address.io.out
+
+  val memory_read_enable = Module(new PipelineRegister(1))
+  memory_read_enable.io.in := io.memory_read_enable
+  memory_read_enable.io.stall := stall
+  memory_read_enable.io.flush := io.flush
+  io.output_memory_read_enable := memory_read_enable.io.out
+
+  val memory_write_enable = Module(new PipelineRegister(1))
+  memory_write_enable.io.in := io.memory_write_enable
+  memory_write_enable.io.stall := stall
+  memory_write_enable.io.flush := io.flush
+  io.output_memory_write_enable := memory_write_enable.io.out
+
+  val csr_read_data = Module(new PipelineRegister())
+  csr_read_data.io.in := io.csr_read_data
+  csr_read_data.io.stall := stall
+  csr_read_data.io.flush := io.flush
+  io.output_csr_read_data := csr_read_data.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_final/IF2ID.scala

@@ -0,0 +1,51 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class IF2ID extends Module {
+  val io = IO(new Bundle {
+    val stall = Input(Bool())
+    val flush = Input(Bool())
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val interrupt_flag = Input(UInt(Parameters.InterruptFlagWidth))
+
+    val output_instruction = Output(UInt(Parameters.DataWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_interrupt_flag = Output(UInt(Parameters.InterruptFlagWidth))
+  })
+
+  val instruction = Module(new PipelineRegister(defaultValue = InstructionsNop.nop))
+  instruction.io.in := io.instruction
+  instruction.io.stall := io.stall
+  instruction.io.flush := io.flush
+  io.output_instruction := instruction.io.out
+
+  val instruction_address = Module(new PipelineRegister(defaultValue = ProgramCounter.EntryAddress))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := io.stall
+  instruction_address.io.flush := io.flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val interrupt_flag = Module(new PipelineRegister(Parameters.InterruptFlagBits))
+  interrupt_flag.io.in := io.interrupt_flag
+  interrupt_flag.io.stall := io.stall
+  interrupt_flag.io.flush := io.flush
+  io.output_interrupt_flag := interrupt_flag.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_final/InstructionDecode.scala

@@ -0,0 +1,229 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+object InstructionTypes {
+  val L = "b0000011".U
+  val I = "b0010011".U
+  val S = "b0100011".U
+  val RM = "b0110011".U
+  val B = "b1100011".U
+}
+
+object Instructions {
+  val lui = "b0110111".U
+  val nop = "b0000001".U
+  val jal = "b1101111".U
+  val jalr = "b1100111".U
+  val auipc = "b0010111".U
+  val csr = "b1110011".U
+  val fence = "b0001111".U
+}
+
+object InstructionsTypeL {
+  val lb = "b000".U
+  val lh = "b001".U
+  val lw = "b010".U
+  val lbu = "b100".U
+  val lhu = "b101".U
+}
+
+object InstructionsTypeI {
+  val addi = 0.U
+  val slli = 1.U
+  val slti = 2.U
+  val sltiu = 3.U
+  val xori = 4.U
+  val sri = 5.U
+  val ori = 6.U
+  val andi = 7.U
+}
+
+object InstructionsTypeS {
+  val sb = "b000".U
+  val sh = "b001".U
+  val sw = "b010".U
+}
+
+object InstructionsTypeR {
+  val add_sub = 0.U
+  val sll = 1.U
+  val slt = 2.U
+  val sltu = 3.U
+  val xor = 4.U
+  val sr = 5.U
+  val or = 6.U
+  val and = 7.U
+}
+
+object InstructionsTypeM {
+  val mul = 0.U
+  val mulh = 1.U
+  val mulhsu = 2.U
+  val mulhum = 3.U
+  val div = 4.U
+  val divu = 5.U
+  val rem = 6.U
+  val remu = 7.U
+}
+
+object InstructionsTypeB {
+  val beq = "b000".U
+  val bne = "b001".U
+  val blt = "b100".U
+  val bge = "b101".U
+  val bltu = "b110".U
+  val bgeu = "b111".U
+}
+
+object InstructionsTypeCSR {
+  val csrrw = "b001".U
+  val csrrs = "b010".U
+  val csrrc = "b011".U
+  val csrrwi = "b101".U
+  val csrrsi = "b110".U
+  val csrrci = "b111".U
+}
+
+object InstructionsNop {
+  val nop = 0x00000013L.U(Parameters.DataWidth)
+}
+
+object InstructionsRet {
+  val mret = 0x30200073L.U(Parameters.DataWidth)
+  val ret = 0x00008067L.U(Parameters.DataWidth)
+}
+
+object InstructionsEnv {
+  val ecall = 0x00000073L.U(Parameters.DataWidth)
+  val ebreak = 0x00100073L.U(Parameters.DataWidth)
+}
+
+object ALUOp1Source {
+  val Register = 0.U(1.W)
+  val InstructionAddress = 1.U(1.W)
+}
+
+object ALUOp2Source {
+  val Register = 0.U(1.W)
+  val Immediate = 1.U(1.W)
+}
+
+object RegWriteSource {
+  val ALUResult = 0.U(2.W)
+  val Memory = 1.U(2.W)
+  val CSR = 2.U(2.W)
+  val NextInstructionAddress = 3.U(2.W)
+}
+
+class InstructionDecode extends Module {
+  val io = IO(new Bundle {
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val reg1_data = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val forward_from_mem = Input(UInt(Parameters.DataWidth))
+    val forward_from_wb = Input(UInt(Parameters.DataWidth))
+    val reg1_forward = Input(UInt(2.W))
+    val reg2_forward = Input(UInt(2.W))
+    val interrupt_assert = Input(Bool())
+    val interrupt_handler_address = Input(UInt(Parameters.AddrWidth))
+
+    val regs_reg1_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_reg2_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val ex_immediate = Output(UInt(Parameters.DataWidth))
+    val ex_aluop1_source = Output(UInt(1.W))
+    val ex_aluop2_source = Output(UInt(1.W))
+    val ex_memory_read_enable = Output(Bool())
+    val ex_memory_write_enable = Output(Bool())
+    val ex_reg_write_source = Output(UInt(2.W))
+    val ex_reg_write_enable = Output(Bool())
+    val ex_reg_write_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val ex_csr_address = Output(UInt(Parameters.CSRRegisterAddrWidth))
+    val ex_csr_write_enable = Output(Bool())
+    val ctrl_jump_instruction = Output(Bool())
+    val clint_jump_flag = Output(Bool())
+    val clint_jump_address = Output(UInt(Parameters.AddrWidth))
+    val if_jump_flag = Output(Bool())
+    val if_jump_address = Output(UInt(Parameters.AddrWidth))
+  })
+  val opcode = io.instruction(6, 0)
+  val funct3 = io.instruction(14, 12)
+  val funct7 = io.instruction(31, 25)
+  val rd = io.instruction(11, 7)
+  val rs1 = io.instruction(19, 15)
+  val rs2 = io.instruction(24, 20)
+
+  io.regs_reg1_read_address := Mux(opcode === Instructions.lui, 0.U(Parameters.PhysicalRegisterAddrWidth), rs1)
+  io.regs_reg2_read_address := rs2
+  io.ex_immediate := MuxLookup(
+    opcode,
+    Cat(Fill(20, io.instruction(31)), io.instruction(31, 20)),
+    IndexedSeq(
+      InstructionTypes.I -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      InstructionTypes.L -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      Instructions.jalr -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      InstructionTypes.S -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 25), io.instruction(11, 7)),
+      InstructionTypes.B -> Cat(Fill(20, io.instruction(31)), io.instruction(7), io.instruction(30, 25), io.instruction(11, 8), 0.U(1.W)),
+      Instructions.lui -> Cat(io.instruction(31, 12), 0.U(12.W)),
+      Instructions.auipc -> Cat(io.instruction(31, 12), 0.U(12.W)),
+      Instructions.jal -> Cat(Fill(12, io.instruction(31)), io.instruction(19, 12), io.instruction(20), io.instruction(30, 21), 0.U(1.W))
+    )
+  )
+  io.ex_aluop1_source := Mux(
+    opcode === Instructions.auipc || opcode === InstructionTypes.B || opcode === Instructions.jal,
+    ALUOp1Source.InstructionAddress,
+    ALUOp1Source.Register
+  )
+  io.ex_aluop2_source := Mux(
+    opcode === InstructionTypes.RM,
+    ALUOp2Source.Register,
+    ALUOp2Source.Immediate
+  )
+  io.ex_memory_read_enable := opcode === InstructionTypes.L
+  io.ex_memory_write_enable := opcode === InstructionTypes.S
+  io.ex_reg_write_source := MuxLookup(
+    opcode,
+    RegWriteSource.ALUResult,
+    IndexedSeq(
+      InstructionTypes.L -> RegWriteSource.Memory,
+      Instructions.csr -> RegWriteSource.CSR,
+      Instructions.jal -> RegWriteSource.NextInstructionAddress,
+      Instructions.jalr -> RegWriteSource.NextInstructionAddress
+    )
+  )
+  io.ex_reg_write_enable := (opcode === InstructionTypes.RM) || (opcode === InstructionTypes.I) ||
+    (opcode === InstructionTypes.L) || (opcode === Instructions.auipc) || (opcode === Instructions.lui) ||
+    (opcode === Instructions.jal) || (opcode === Instructions.jalr) || (opcode === Instructions.csr)
+  io.ex_reg_write_address := io.instruction(11, 7)
+  io.ex_csr_address := io.instruction(31, 20)
+  io.ex_csr_write_enable := (opcode === Instructions.csr) && (
+    funct3 === InstructionsTypeCSR.csrrw || funct3 === InstructionsTypeCSR.csrrwi ||
+      funct3 === InstructionsTypeCSR.csrrs || funct3 === InstructionsTypeCSR.csrrsi ||
+      funct3 === InstructionsTypeCSR.csrrc || funct3 === InstructionsTypeCSR.csrrci
+    )
+
+  // Lab3(Final)
+  io.ctrl_jump_instruction := false.B
+  io.clint_jump_flag := false.B
+  io.clint_jump_address := 0.U
+  io.if_jump_flag := false.B
+  io.if_jump_address := 0.U
+  // Lab3(Final) End
+}

lab3/src/main/scala/riscv/core/fivestage_final/InstructionFetch.scala

@@ -0,0 +1,48 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import chisel3.util.MuxCase
+import riscv.Parameters
+
+object ProgramCounter {
+  val EntryAddress = Parameters.EntryAddress
+}
+
+class InstructionFetch extends Module {
+  val io = IO(new Bundle {
+    val stall_flag_ctrl = Input(Bool())
+    val jump_flag_id = Input(Bool())
+    val jump_address_id = Input(UInt(Parameters.AddrWidth))
+    val rom_instruction = Input(UInt(Parameters.DataWidth))
+    val instruction_valid = Input(Bool())
+
+    val instruction_address = Output(UInt(Parameters.AddrWidth))
+    val id_instruction = Output(UInt(Parameters.InstructionWidth))
+  })
+  val pc = RegInit(ProgramCounter.EntryAddress)
+
+  pc := MuxCase(
+    pc + 4.U,
+    IndexedSeq(
+      (io.jump_flag_id && !io.stall_flag_ctrl) -> io.jump_address_id,
+      (io.stall_flag_ctrl || !io.instruction_valid) -> pc
+    )
+  )
+
+  io.instruction_address := pc
+  io.id_instruction := Mux(io.instruction_valid, io.rom_instruction, InstructionsNop.nop)
+}

lab3/src/main/scala/riscv/core/fivestage_final/MEM2WB.scala

@@ -0,0 +1,83 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class MEM2WB extends Module {
+  val io = IO(new Bundle() {
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val regs_write_enable = Input(Bool())
+    val regs_write_source = Input(UInt(2.W))
+    val regs_write_address = Input(UInt(Parameters.AddrWidth))
+    val memory_read_data = Input(UInt(Parameters.DataWidth))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_alu_result = Output(UInt(Parameters.DataWidth))
+    val output_regs_write_enable = Output(Bool())
+    val output_regs_write_source = Output(UInt(2.W))
+    val output_regs_write_address = Output(UInt(Parameters.AddrWidth))
+    val output_memory_read_data = Output(UInt(Parameters.DataWidth))
+    val output_csr_read_data = Output(UInt(Parameters.DataWidth))
+  })
+  val stall = false.B
+  val flush = false.B
+
+  val alu_result = Module(new PipelineRegister())
+  alu_result.io.in := io.alu_result
+  alu_result.io.stall := stall
+  alu_result.io.flush := flush
+  io.output_alu_result := alu_result.io.out
+
+  val memory_read_data = Module(new PipelineRegister())
+  memory_read_data.io.in := io.memory_read_data
+  memory_read_data.io.stall := stall
+  memory_read_data.io.flush := flush
+  io.output_memory_read_data := memory_read_data.io.out
+
+  val regs_write_enable = Module(new PipelineRegister(1))
+  regs_write_enable.io.in := io.regs_write_enable
+  regs_write_enable.io.stall := stall
+  regs_write_enable.io.flush := flush
+  io.output_regs_write_enable := regs_write_enable.io.out
+
+  val regs_write_source = Module(new PipelineRegister(2))
+  regs_write_source.io.in := io.regs_write_source
+  regs_write_source.io.stall := stall
+  regs_write_source.io.flush := flush
+  io.output_regs_write_source := regs_write_source.io.out
+
+  val regs_write_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_write_address.io.in := io.regs_write_address
+  regs_write_address.io.stall := stall
+  regs_write_address.io.flush := flush
+  io.output_regs_write_address := regs_write_address.io.out
+
+  val instruction_address = Module(new PipelineRegister(Parameters.InstructionBits))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val csr_read_data = Module(new PipelineRegister())
+  csr_read_data.io.in := io.csr_read_data
+  csr_read_data.io.stall := stall
+  csr_read_data.io.flush := flush
+  io.output_csr_read_data := csr_read_data.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_final/MemoryAccess.scala

@@ -0,0 +1,109 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import chisel3.util._
+import peripheral.RAMBundle
+import riscv.Parameters
+
+class MemoryAccess extends Module {
+  val io = IO(new Bundle() {
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val memory_read_enable = Input(Bool())
+    val memory_write_enable = Input(Bool())
+    val funct3 = Input(UInt(3.W))
+    val regs_write_source = Input(UInt(2.W))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val wb_memory_read_data = Output(UInt(Parameters.DataWidth))
+    val forward_data = Output(UInt(Parameters.DataWidth))
+
+    val bundle = Flipped(new RAMBundle)
+  })
+  val mem_address_index = io.alu_result(log2Up(Parameters.WordSize) - 1, 0).asUInt
+
+  io.bundle.write_enable := io.memory_write_enable
+  io.bundle.write_data := 0.U
+  io.bundle.address := io.alu_result
+  io.bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(false.B))
+  io.wb_memory_read_data := 0.U
+
+  when(io.memory_read_enable) {
+    val data = io.bundle.read_data
+    io.wb_memory_read_data := MuxLookup(
+      io.funct3,
+      0.U,
+      IndexedSeq(
+        InstructionsTypeL.lb -> MuxLookup(
+          mem_address_index,
+          Cat(Fill(24, data(31)), data(31, 24)),
+          IndexedSeq(
+            0.U -> Cat(Fill(24, data(7)), data(7, 0)),
+            1.U -> Cat(Fill(24, data(15)), data(15, 8)),
+            2.U -> Cat(Fill(24, data(23)), data(23, 16))
+          )
+        ),
+        InstructionsTypeL.lbu -> MuxLookup(
+          mem_address_index,
+          Cat(Fill(24, 0.U), data(31, 24)),
+          IndexedSeq(
+            0.U -> Cat(Fill(24, 0.U), data(7, 0)),
+            1.U -> Cat(Fill(24, 0.U), data(15, 8)),
+            2.U -> Cat(Fill(24, 0.U), data(23, 16))
+          )
+        ),
+        InstructionsTypeL.lh -> Mux(
+          mem_address_index === 0.U,
+          Cat(Fill(16, data(15)), data(15, 0)),
+          Cat(Fill(16, data(31)), data(31, 16))
+        ),
+        InstructionsTypeL.lhu -> Mux(
+          mem_address_index === 0.U,
+          Cat(Fill(16, 0.U), data(15, 0)),
+          Cat(Fill(16, 0.U), data(31, 16))
+        ),
+        InstructionsTypeL.lw -> data
+      )
+    )
+  }.elsewhen(io.memory_write_enable) {
+    io.bundle.write_data := io.reg2_data
+    io.bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(false.B))
+    when(io.funct3 === InstructionsTypeS.sb) {
+      io.bundle.write_strobe(mem_address_index) := true.B
+      io.bundle.write_data := io.reg2_data(Parameters.ByteBits, 0) << (mem_address_index << log2Up(Parameters.ByteBits).U)
+    }.elsewhen(io.funct3 === InstructionsTypeS.sh) {
+      when(mem_address_index === 0.U) {
+        for (i <- 0 until Parameters.WordSize / 2) {
+          io.bundle.write_strobe(i) := true.B
+        }
+        io.bundle.write_data := io.reg2_data(Parameters.WordSize / 2 * Parameters.ByteBits, 0)
+      }.otherwise {
+        for (i <- Parameters.WordSize / 2 until Parameters.WordSize) {
+          io.bundle.write_strobe(i) := true.B
+        }
+        io.bundle.write_data := io.reg2_data(Parameters.WordSize / 2 * Parameters.ByteBits, 0) << (Parameters
+          .WordSize / 2 * Parameters.ByteBits)
+      }
+    }.elsewhen(io.funct3 === InstructionsTypeS.sw) {
+      for (i <- 0 until Parameters.WordSize) {
+        io.bundle.write_strobe(i) := true.B
+      }
+    }
+  }
+
+  io.forward_data := Mux(io.regs_write_source === RegWriteSource.CSR, io.csr_read_data, io.alu_result)
+}

lab3/src/main/scala/riscv/core/fivestage_final/WriteBack.scala

@@ -0,0 +1,40 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_final
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+class WriteBack extends Module {
+  val io = IO(new Bundle() {
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val memory_read_data = Input(UInt(Parameters.DataWidth))
+    val regs_write_source = Input(UInt(2.W))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val regs_write_data = Output(UInt(Parameters.DataWidth))
+  })
+  io.regs_write_data := MuxLookup(
+    io.regs_write_source,
+    io.alu_result,
+    IndexedSeq(
+      RegWriteSource.Memory -> io.memory_read_data,
+      RegWriteSource.CSR -> io.csr_read_data,
+      RegWriteSource.NextInstructionAddress -> (io.instruction_address + 4.U)
+    )
+  )
+}

lab3/src/main/scala/riscv/core/fivestage_forward/CLINT.scala

@@ -0,0 +1,103 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import chisel3.util.MuxLookup
+import riscv.Parameters
+
+object InterruptStatus {
+  val None = 0x0.U(8.W)
+  val Timer0 = 0x1.U(8.W)
+  val Ret = 0xFF.U(8.W)
+}
+
+class CSRDirectAccessBundle extends Bundle {
+  val mstatus = Input(UInt(Parameters.DataWidth))
+  val mepc = Input(UInt(Parameters.DataWidth))
+  val mcause = Input(UInt(Parameters.DataWidth))
+  val mtvec = Input(UInt(Parameters.DataWidth))
+
+  val mstatus_write_data = Output(UInt(Parameters.DataWidth))
+  val mepc_write_data = Output(UInt(Parameters.DataWidth))
+  val mcause_write_data = Output(UInt(Parameters.DataWidth))
+
+  val direct_write_enable = Output(Bool())
+}
+
+// Core Local Interrupt Controller
+class CLINT extends Module {
+  val io = IO(new Bundle {
+    val interrupt_flag = Input(UInt(Parameters.InterruptFlagWidth))
+
+    val instruction_ex = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address_if = Input(UInt(Parameters.AddrWidth))
+    val instruction_address_id = Input(UInt(Parameters.AddrWidth))
+
+    val jump_flag = Input(Bool())
+    val jump_address = Input(UInt(Parameters.AddrWidth))
+
+    val ex_interrupt_handler_address = Output(UInt(Parameters.AddrWidth))
+    val ex_interrupt_assert = Output(Bool())
+
+    val csr_bundle = new CSRDirectAccessBundle
+  })
+  val interrupt_enable = io.csr_bundle.mstatus(3)
+  val jumpping = RegNext(io.jump_flag || io.ex_interrupt_assert)
+  val instruction_address = Mux(
+    io.jump_flag,
+    io.jump_address,
+    Mux(jumpping, io.instruction_address_if, io.instruction_address_id)
+  )
+  val mstatus_disable_interrupt = io.csr_bundle.mstatus(31, 4) ## 0.U(1.W) ## io.csr_bundle.mstatus(2, 0)
+  val mstatus_recover_interrupt = io.csr_bundle.mstatus(31, 4) ## io.csr_bundle.mstatus(7) ## io.csr_bundle.mstatus(2, 0)
+
+  when(io.instruction_ex === InstructionsEnv.ecall || io.instruction_ex === InstructionsEnv.ebreak) {
+    io.csr_bundle.mstatus_write_data := mstatus_disable_interrupt
+    io.csr_bundle.mepc_write_data := instruction_address
+    io.csr_bundle.mcause_write_data := MuxLookup(
+      io.instruction_ex,
+      10.U,
+      IndexedSeq(
+        InstructionsEnv.ecall -> 11.U,
+        InstructionsEnv.ebreak -> 3.U,
+      )
+    )
+    io.csr_bundle.direct_write_enable := true.B
+    io.ex_interrupt_assert := true.B
+    io.ex_interrupt_handler_address := io.csr_bundle.mtvec
+  }.elsewhen(io.interrupt_flag =/= InterruptStatus.None && interrupt_enable) {
+    io.csr_bundle.mstatus_write_data := mstatus_disable_interrupt
+    io.csr_bundle.mepc_write_data := instruction_address
+    io.csr_bundle.mcause_write_data := Mux(io.interrupt_flag(0), 0x80000007L.U, 0x8000000BL.U)
+    io.csr_bundle.direct_write_enable := true.B
+    io.ex_interrupt_assert := true.B
+    io.ex_interrupt_handler_address := io.csr_bundle.mtvec
+  }.elsewhen(io.instruction_ex === InstructionsRet.mret) {
+    io.csr_bundle.mstatus_write_data := mstatus_recover_interrupt
+    io.csr_bundle.mepc_write_data := io.csr_bundle.mepc
+    io.csr_bundle.mcause_write_data := io.csr_bundle.mcause
+    io.csr_bundle.direct_write_enable := true.B
+    io.ex_interrupt_assert := true.B
+    io.ex_interrupt_handler_address := io.csr_bundle.mepc
+  }.otherwise {
+    io.csr_bundle.mstatus_write_data := io.csr_bundle.mstatus
+    io.csr_bundle.mepc_write_data := io.csr_bundle.mepc
+    io.csr_bundle.mcause_write_data := io.csr_bundle.mcause
+    io.csr_bundle.direct_write_enable := false.B
+    io.ex_interrupt_assert := false.B
+    io.ex_interrupt_handler_address := 0.U
+  }
+}

lab3/src/main/scala/riscv/core/fivestage_forward/CPU.scala

@@ -0,0 +1,158 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.{CPUBundle, CSR, RegisterFile}
+
+class CPU extends Module {
+  val io = IO(new CPUBundle)
+
+  val ctrl = Module(new Control)
+  val regs = Module(new RegisterFile)
+  val inst_fetch = Module(new InstructionFetch)
+  val if2id = Module(new IF2ID)
+  val id = Module(new InstructionDecode)
+  val id2ex = Module(new ID2EX)
+  val ex = Module(new Execute)
+  val ex2mem = Module(new EX2MEM)
+  val mem = Module(new MemoryAccess)
+  val mem2wb = Module(new MEM2WB)
+  val wb = Module(new WriteBack)
+  val forwarding = Module(new Forwarding)
+  val clint = Module(new CLINT)
+  val csr_regs = Module(new CSR)
+
+  ctrl.io.jump_flag := ex.io.if_jump_flag
+  ctrl.io.rs1_id := id.io.regs_reg1_read_address
+  ctrl.io.rs2_id := id.io.regs_reg2_read_address
+  ctrl.io.memory_read_enable_ex := id2ex.io.output_memory_read_enable
+  ctrl.io.rd_ex := id2ex.io.output_regs_write_address
+
+  regs.io.write_enable := mem2wb.io.output_regs_write_enable
+  regs.io.write_address := mem2wb.io.output_regs_write_address
+  regs.io.write_data := wb.io.regs_write_data
+  regs.io.read_address1 := id.io.regs_reg1_read_address
+  regs.io.read_address2 := id.io.regs_reg2_read_address
+
+  regs.io.debug_read_address := io.debug_read_address
+  io.debug_read_data := regs.io.debug_read_data
+
+  io.instruction_address := inst_fetch.io.instruction_address
+  inst_fetch.io.stall_flag_ctrl := ctrl.io.pc_stall
+  inst_fetch.io.jump_flag_id := ex.io.if_jump_flag
+  inst_fetch.io.jump_address_id := ex.io.if_jump_address
+  inst_fetch.io.rom_instruction := io.instruction
+  inst_fetch.io.instruction_valid := io.instruction_valid
+
+  if2id.io.stall := ctrl.io.if_stall
+  if2id.io.flush := ctrl.io.if_flush
+  if2id.io.instruction := inst_fetch.io.id_instruction
+  if2id.io.instruction_address := inst_fetch.io.instruction_address
+  if2id.io.interrupt_flag := io.interrupt_flag
+
+  id.io.instruction := if2id.io.output_instruction
+
+  id2ex.io.flush := ctrl.io.id_flush
+  id2ex.io.instruction := if2id.io.output_instruction
+  id2ex.io.instruction_address := if2id.io.output_instruction_address
+  id2ex.io.reg1_data := regs.io.read_data1
+  id2ex.io.reg2_data := regs.io.read_data2
+  id2ex.io.regs_reg1_read_address := id.io.regs_reg1_read_address
+  id2ex.io.regs_reg2_read_address := id.io.regs_reg2_read_address
+  id2ex.io.regs_write_enable := id.io.ex_reg_write_enable
+  id2ex.io.regs_write_address := id.io.ex_reg_write_address
+  id2ex.io.regs_write_source := id.io.ex_reg_write_source
+  id2ex.io.immediate := id.io.ex_immediate
+  id2ex.io.aluop1_source := id.io.ex_aluop1_source
+  id2ex.io.aluop2_source := id.io.ex_aluop2_source
+  id2ex.io.csr_write_enable := id.io.ex_csr_write_enable
+  id2ex.io.csr_address := id.io.ex_csr_address
+  id2ex.io.memory_read_enable := id.io.ex_memory_read_enable
+  id2ex.io.memory_write_enable := id.io.ex_memory_write_enable
+  id2ex.io.csr_read_data := csr_regs.io.id_reg_read_data
+
+  ex.io.instruction := id2ex.io.output_instruction
+  ex.io.instruction_address := id2ex.io.output_instruction_address
+  ex.io.reg1_data := id2ex.io.output_reg1_data
+  ex.io.reg2_data := id2ex.io.output_reg2_data
+  ex.io.immediate_id := id2ex.io.output_immediate
+  ex.io.aluop1_source_id := id2ex.io.output_aluop1_source
+  ex.io.aluop2_source_id := id2ex.io.output_aluop2_source
+  ex.io.csr_read_data_id := id2ex.io.output_csr_read_data
+  ex.io.forward_from_mem := mem.io.forward_data
+  ex.io.forward_from_wb := wb.io.regs_write_data
+  ex.io.reg1_forward := forwarding.io.reg1_forward_ex
+  ex.io.reg2_forward := forwarding.io.reg2_forward_ex
+  ex.io.interrupt_assert_clint := clint.io.ex_interrupt_assert
+  ex.io.interrupt_handler_address_clint := clint.io.ex_interrupt_handler_address
+
+  ex2mem.io.regs_write_enable := id2ex.io.output_regs_write_enable
+  ex2mem.io.regs_write_source := id2ex.io.output_regs_write_source
+  ex2mem.io.regs_write_address := id2ex.io.output_regs_write_address
+  ex2mem.io.instruction_address := id2ex.io.output_instruction_address
+  ex2mem.io.funct3 := id2ex.io.output_instruction(14, 12)
+  ex2mem.io.reg2_data := ex.io.mem_reg2_data
+  ex2mem.io.memory_read_enable := id2ex.io.output_memory_read_enable
+  ex2mem.io.memory_write_enable := id2ex.io.output_memory_write_enable
+  ex2mem.io.alu_result := ex.io.mem_alu_result
+  ex2mem.io.csr_read_data := id2ex.io.output_csr_read_data
+
+  mem.io.alu_result := ex2mem.io.output_alu_result
+  mem.io.reg2_data := ex2mem.io.output_reg2_data
+  mem.io.memory_read_enable := ex2mem.io.output_memory_read_enable
+  mem.io.memory_write_enable := ex2mem.io.output_memory_write_enable
+  mem.io.funct3 := ex2mem.io.output_funct3
+  mem.io.regs_write_source := ex2mem.io.output_regs_write_source
+  mem.io.csr_read_data := ex2mem.io.output_csr_read_data
+  io.device_select := mem.io.bundle.address(Parameters.AddrBits - 1, Parameters.AddrBits - Parameters.SlaveDeviceCountBits)
+  io.memory_bundle <> mem.io.bundle
+  io.memory_bundle.address := 0.U(Parameters.SlaveDeviceCountBits.W) ## mem.io.bundle.address(Parameters.AddrBits - 1 - Parameters.SlaveDeviceCountBits, 0)
+
+  mem2wb.io.instruction_address := ex2mem.io.output_instruction_address
+  mem2wb.io.alu_result := ex2mem.io.output_alu_result
+  mem2wb.io.regs_write_enable := ex2mem.io.output_regs_write_enable
+  mem2wb.io.regs_write_source := ex2mem.io.output_regs_write_source
+  mem2wb.io.regs_write_address := ex2mem.io.output_regs_write_address
+  mem2wb.io.memory_read_data := mem.io.wb_memory_read_data
+  mem2wb.io.csr_read_data := ex2mem.io.output_csr_read_data
+
+  wb.io.instruction_address := mem2wb.io.output_instruction_address
+  wb.io.alu_result := mem2wb.io.output_alu_result
+  wb.io.memory_read_data := mem2wb.io.output_memory_read_data
+  wb.io.regs_write_source := mem2wb.io.output_regs_write_source
+  wb.io.csr_read_data := mem2wb.io.output_csr_read_data
+
+  forwarding.io.rs1_ex := id2ex.io.output_regs_reg1_read_address
+  forwarding.io.rs2_ex := id2ex.io.output_regs_reg2_read_address
+  forwarding.io.rd_mem := ex2mem.io.output_regs_write_address
+  forwarding.io.reg_write_enable_mem := ex2mem.io.output_regs_write_enable
+  forwarding.io.rd_wb := mem2wb.io.output_regs_write_address
+  forwarding.io.reg_write_enable_wb := mem2wb.io.output_regs_write_enable
+
+  clint.io.instruction_address_if := inst_fetch.io.instruction_address
+  clint.io.instruction_address_id := if2id.io.output_instruction_address
+  clint.io.instruction_ex := id2ex.io.output_instruction
+  clint.io.jump_flag := ex.io.clint_jump_flag
+  clint.io.jump_address := ex.io.clint_jump_address
+  clint.io.interrupt_flag := if2id.io.output_interrupt_flag
+  clint.io.csr_bundle <> csr_regs.io.clint_access_bundle
+
+  csr_regs.io.reg_read_address_id := id.io.ex_csr_address
+  csr_regs.io.reg_write_enable_ex := id2ex.io.output_csr_write_enable
+  csr_regs.io.reg_write_address_ex := id2ex.io.output_csr_address
+  csr_regs.io.reg_write_data_ex := ex.io.csr_write_data
+}

lab3/src/main/scala/riscv/core/fivestage_forward/Control.scala

@@ -0,0 +1,40 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import riscv.Parameters
+
+class Control extends Module {
+  val io = IO(new Bundle {
+    val jump_flag = Input(Bool())
+    val rs1_id = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val rs2_id = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val memory_read_enable_ex = Input(Bool())
+    val rd_ex = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+
+    val if_flush = Output(Bool())
+    val id_flush = Output(Bool())
+    val pc_stall = Output(Bool())
+    val if_stall = Output(Bool())
+  })
+
+  // Lab3(Forward)
+  io.if_flush := false.B
+  io.id_flush := false.B
+  io.pc_stall := false.B
+  io.if_stall := false.B
+  // Lab3(Forward) End
+}

lab3/src/main/scala/riscv/core/fivestage_forward/EX2MEM.scala

@@ -0,0 +1,108 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class EX2MEM extends Module {
+  val io = IO(new Bundle() {
+    val regs_write_enable = Input(Bool())
+    val regs_write_source = Input(UInt(2.W))
+    val regs_write_address = Input(UInt(Parameters.AddrWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val funct3 = Input(UInt(3.W))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val memory_read_enable = Input(Bool())
+    val memory_write_enable = Input(Bool())
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val output_regs_write_enable = Output(Bool())
+    val output_regs_write_source = Output(UInt(2.W))
+    val output_regs_write_address = Output(UInt(Parameters.AddrWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_funct3 = Output(UInt(Parameters.DataWidth))
+    val output_reg2_data = Output(UInt(Parameters.DataWidth))
+    val output_memory_read_enable = Output(Bool())
+    val output_memory_write_enable = Output(Bool())
+    val output_alu_result = Output(UInt(Parameters.DataWidth))
+    val output_csr_read_data = Output(UInt(Parameters.DataWidth))
+  })
+
+  val stall = false.B
+  val flush = false.B
+
+  val regs_write_enable = Module(new PipelineRegister(1))
+  regs_write_enable.io.in := io.regs_write_enable
+  regs_write_enable.io.stall := stall
+  regs_write_enable.io.flush := flush
+  io.output_regs_write_enable := regs_write_enable.io.out
+
+  val regs_write_source = Module(new PipelineRegister(2))
+  regs_write_source.io.in := io.regs_write_source
+  regs_write_source.io.stall := stall
+  regs_write_source.io.flush := flush
+  io.output_regs_write_source := regs_write_source.io.out
+
+  val regs_write_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_write_address.io.in := io.regs_write_address
+  regs_write_address.io.stall := stall
+  regs_write_address.io.flush := flush
+  io.output_regs_write_address := regs_write_address.io.out
+
+  val instruction_address = Module(new PipelineRegister(Parameters.AddrBits))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val funct3 = Module(new PipelineRegister(3))
+  funct3.io.in := io.funct3
+  funct3.io.stall := stall
+  funct3.io.flush := flush
+  io.output_funct3 := funct3.io.out
+
+  val reg2_data = Module(new PipelineRegister())
+  reg2_data.io.in := io.reg2_data
+  reg2_data.io.stall := stall
+  reg2_data.io.flush := flush
+  io.output_reg2_data := reg2_data.io.out
+
+  val alu_result = Module(new PipelineRegister())
+  alu_result.io.in := io.alu_result
+  alu_result.io.stall := stall
+  alu_result.io.flush := flush
+  io.output_alu_result := alu_result.io.out
+
+  val memory_read_enable = Module(new PipelineRegister(1))
+  memory_read_enable.io.in := io.memory_read_enable
+  memory_read_enable.io.stall := stall
+  memory_read_enable.io.flush := flush
+  io.output_memory_read_enable := memory_read_enable.io.out
+
+  val memory_write_enable = Module(new PipelineRegister(1))
+  memory_write_enable.io.in := io.memory_write_enable
+  memory_write_enable.io.stall := stall
+  memory_write_enable.io.flush := flush
+  io.output_memory_write_enable := memory_write_enable.io.out
+
+  val csr_read_data = Module(new PipelineRegister())
+  csr_read_data.io.in := io.csr_read_data
+  csr_read_data.io.stall := stall
+  csr_read_data.io.flush := flush
+  io.output_csr_read_data := csr_read_data.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_forward/Execute.scala

@@ -0,0 +1,111 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+import riscv.core.{ALU, ALUControl}
+
+
+class Execute extends Module {
+  val io = IO(new Bundle {
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val reg1_data = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val immediate_id = Input(UInt(Parameters.DataWidth))
+    val aluop1_source_id = Input(UInt(1.W))
+    val aluop2_source_id = Input(UInt(1.W))
+    val csr_read_data_id = Input(UInt(Parameters.DataWidth))
+    val forward_from_mem = Input(UInt(Parameters.DataWidth))
+    val forward_from_wb = Input(UInt(Parameters.DataWidth))
+    val reg1_forward = Input(UInt(2.W))
+    val reg2_forward = Input(UInt(2.W))
+    val interrupt_assert_clint = Input(Bool())
+    val interrupt_handler_address_clint = Input(UInt(Parameters.AddrWidth))
+
+    val mem_alu_result = Output(UInt(Parameters.DataWidth))
+    val mem_reg2_data = Output(UInt(Parameters.DataWidth))
+    val csr_write_data = Output(UInt(Parameters.DataWidth))
+    val if_jump_flag = Output(Bool())
+    val if_jump_address = Output(UInt(Parameters.AddrWidth))
+    val clint_jump_flag = Output(Bool())
+    val clint_jump_address = Output(UInt(Parameters.AddrWidth))
+  })
+
+  val opcode = io.instruction(6, 0)
+  val funct3 = io.instruction(14, 12)
+  val funct7 = io.instruction(31, 25)
+  val uimm = io.instruction(19, 15)
+
+  // ALU compute
+  val alu = Module(new ALU)
+  val alu_ctrl = Module(new ALUControl)
+
+  alu_ctrl.io.opcode := opcode
+  alu_ctrl.io.funct3 := funct3
+  alu_ctrl.io.funct7 := funct7
+  alu.io.func := alu_ctrl.io.alu_funct
+
+  // Lab3(Forward)
+  val reg1_data = 0.U
+  val reg2_data = 0.U
+  // Lab3(Forward) End
+
+  alu.io.op1 := Mux(
+    io.aluop1_source_id === ALUOp1Source.InstructionAddress,
+    io.instruction_address,
+    reg1_data
+  )
+  alu.io.op2 := Mux(
+    io.aluop2_source_id === ALUOp2Source.Immediate,
+    io.immediate_id,
+    reg2_data
+  )
+  io.mem_alu_result := alu.io.result
+  io.mem_reg2_data := reg2_data
+  io.csr_write_data := MuxLookup(funct3, 0.U, IndexedSeq(
+    InstructionsTypeCSR.csrrw -> reg1_data,
+    InstructionsTypeCSR.csrrc -> io.csr_read_data_id.&((~reg1_data).asUInt),
+    InstructionsTypeCSR.csrrs -> io.csr_read_data_id.|(reg1_data),
+    InstructionsTypeCSR.csrrwi -> Cat(0.U(27.W), uimm),
+    InstructionsTypeCSR.csrrci -> io.csr_read_data_id.&((~Cat(0.U(27.W), uimm)).asUInt),
+    InstructionsTypeCSR.csrrsi -> io.csr_read_data_id.|(Cat(0.U(27.W), uimm)),
+  ))
+
+  // jump and interrupt
+  val instruction_jump_flag = (opcode === Instructions.jal) ||
+    (opcode === Instructions.jalr) ||
+    (opcode === InstructionTypes.B) && MuxLookup(
+      funct3,
+      false.B,
+      IndexedSeq(
+        InstructionsTypeB.beq -> (reg1_data === reg2_data),
+        InstructionsTypeB.bne -> (reg1_data =/= reg2_data),
+        InstructionsTypeB.blt -> (reg1_data.asSInt < reg2_data.asSInt),
+        InstructionsTypeB.bge -> (reg1_data.asSInt >= reg2_data.asSInt),
+        InstructionsTypeB.bltu -> (reg1_data.asUInt < reg2_data.asUInt),
+        InstructionsTypeB.bgeu -> (reg1_data.asUInt >= reg2_data.asUInt)
+      )
+    )
+  io.clint_jump_flag := instruction_jump_flag
+  io.clint_jump_address := alu.io.result
+  io.if_jump_flag := io.interrupt_assert_clint || instruction_jump_flag
+  io.if_jump_address := Mux(io.interrupt_assert_clint,
+    io.interrupt_handler_address_clint,
+    alu.io.result
+  )
+}

lab3/src/main/scala/riscv/core/fivestage_forward/Forwarding.scala

@@ -0,0 +1,44 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import riscv.Parameters
+
+object ForwardingType {
+  val NoForward = 0.U(2.W)
+  val ForwardFromMEM = 1.U(2.W)
+  val ForwardFromWB = 2.U(2.W)
+}
+
+class Forwarding extends Module {
+  val io = IO(new Bundle() {
+    val rs1_ex = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val rs2_ex = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val rd_mem = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val reg_write_enable_mem = Input(Bool())
+    val rd_wb = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val reg_write_enable_wb = Input(Bool())
+
+    // Forwarding Type
+    val reg1_forward_ex = Output(UInt(2.W))
+    val reg2_forward_ex = Output(UInt(2.W))
+  })
+
+  // Lab3(Forward)
+  io.reg1_forward_ex := 0.U
+  io.reg2_forward_ex := 0.U
+  // Lab3(Forward) End
+}

lab3/src/main/scala/riscv/core/fivestage_forward/ID2EX.scala

@@ -0,0 +1,164 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class ID2EX extends Module {
+  val io = IO(new Bundle {
+    val flush = Input(Bool())
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val regs_reg1_read_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_reg2_read_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_write_enable = Input(Bool())
+    val regs_write_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_write_source = Input(UInt(2.W))
+    val reg1_data = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val immediate = Input(UInt(Parameters.DataWidth))
+    val aluop1_source = Input(UInt(1.W))
+    val aluop2_source = Input(UInt(1.W))
+    val csr_write_enable = Input(Bool())
+    val csr_address = Input(UInt(Parameters.CSRRegisterAddrWidth))
+    val memory_read_enable = Input(Bool())
+    val memory_write_enable = Input(Bool())
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val output_instruction = Output(UInt(Parameters.DataWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_regs_reg1_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val output_regs_reg2_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val output_regs_write_enable = Output(Bool())
+    val output_regs_write_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val output_regs_write_source = Output(UInt(2.W))
+    val output_reg1_data = Output(UInt(Parameters.DataWidth))
+    val output_reg2_data = Output(UInt(Parameters.DataWidth))
+    val output_immediate = Output(UInt(Parameters.DataWidth))
+    val output_aluop1_source = Output(UInt(1.W))
+    val output_aluop2_source = Output(UInt(1.W))
+    val output_csr_write_enable = Output(Bool())
+    val output_csr_address = Output(UInt(Parameters.CSRRegisterAddrWidth))
+    val output_memory_read_enable = Output(Bool())
+    val output_memory_write_enable = Output(Bool())
+    val output_csr_read_data = Output(UInt(Parameters.DataWidth))
+  })
+
+  val stall = false.B
+
+  val instruction = Module(new PipelineRegister(defaultValue = InstructionsNop.nop))
+  instruction.io.in := io.instruction
+  instruction.io.stall := stall
+  instruction.io.flush := io.flush
+  io.output_instruction := instruction.io.out
+
+  val instruction_address = Module(new PipelineRegister(defaultValue = ProgramCounter.EntryAddress))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := io.flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val regs_reg1_read_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_reg1_read_address.io.in := io.regs_reg1_read_address
+  regs_reg1_read_address.io.stall := stall
+  regs_reg1_read_address.io.flush := io.flush
+  io.output_regs_reg1_read_address := regs_reg1_read_address.io.out
+
+  val regs_reg2_read_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_reg2_read_address.io.in := io.regs_reg2_read_address
+  regs_reg2_read_address.io.stall := stall
+  regs_reg2_read_address.io.flush := io.flush
+  io.output_regs_reg2_read_address := regs_reg2_read_address.io.out
+
+  val regs_write_enable = Module(new PipelineRegister(1))
+  regs_write_enable.io.in := io.regs_write_enable
+  regs_write_enable.io.stall := stall
+  regs_write_enable.io.flush := io.flush
+  io.output_regs_write_enable := regs_write_enable.io.out
+
+  val regs_write_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_write_address.io.in := io.regs_write_address
+  regs_write_address.io.stall := stall
+  regs_write_address.io.flush := io.flush
+  io.output_regs_write_address := regs_write_address.io.out
+
+  val regs_write_source = Module(new PipelineRegister(2))
+  regs_write_source.io.in := io.regs_write_source
+  regs_write_source.io.stall := stall
+  regs_write_source.io.flush := io.flush
+  io.output_regs_write_source := regs_write_source.io.out
+
+  val reg1_data = Module(new PipelineRegister())
+  reg1_data.io.in := io.reg1_data
+  reg1_data.io.stall := stall
+  reg1_data.io.flush := io.flush
+  io.output_reg1_data := reg1_data.io.out
+
+  val reg2_data = Module(new PipelineRegister())
+  reg2_data.io.in := io.reg2_data
+  reg2_data.io.stall := stall
+  reg2_data.io.flush := io.flush
+  io.output_reg2_data := reg2_data.io.out
+
+  val immediate = Module(new PipelineRegister())
+  immediate.io.in := io.immediate
+  immediate.io.stall := stall
+  immediate.io.flush := io.flush
+  io.output_immediate := immediate.io.out
+
+  val aluop1_source = Module(new PipelineRegister(1))
+  aluop1_source.io.in := io.aluop1_source
+  aluop1_source.io.stall := stall
+  aluop1_source.io.flush := io.flush
+  io.output_aluop1_source := aluop1_source.io.out
+
+  val aluop2_source = Module(new PipelineRegister(1))
+  aluop2_source.io.in := io.aluop2_source
+  aluop2_source.io.stall := stall
+  aluop2_source.io.flush := io.flush
+  io.output_aluop2_source := aluop2_source.io.out
+
+  val csr_write_enable = Module(new PipelineRegister(1))
+  csr_write_enable.io.in := io.csr_write_enable
+  csr_write_enable.io.stall := stall
+  csr_write_enable.io.flush := io.flush
+  io.output_csr_write_enable := csr_write_enable.io.out
+
+  val csr_address = Module(new PipelineRegister(Parameters.CSRRegisterAddrBits))
+  csr_address.io.in := io.csr_address
+  csr_address.io.stall := stall
+  csr_address.io.flush := io.flush
+  io.output_csr_address := csr_address.io.out
+
+  val memory_read_enable = Module(new PipelineRegister(1))
+  memory_read_enable.io.in := io.memory_read_enable
+  memory_read_enable.io.stall := stall
+  memory_read_enable.io.flush := io.flush
+  io.output_memory_read_enable := memory_read_enable.io.out
+
+  val memory_write_enable = Module(new PipelineRegister(1))
+  memory_write_enable.io.in := io.memory_write_enable
+  memory_write_enable.io.stall := stall
+  memory_write_enable.io.flush := io.flush
+  io.output_memory_write_enable := memory_write_enable.io.out
+
+  val csr_read_data = Module(new PipelineRegister())
+  csr_read_data.io.in := io.csr_read_data
+  csr_read_data.io.stall := stall
+  csr_read_data.io.flush := io.flush
+  io.output_csr_read_data := csr_read_data.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_forward/IF2ID.scala

@@ -0,0 +1,51 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class IF2ID extends Module {
+  val io = IO(new Bundle {
+    val stall = Input(Bool())
+    val flush = Input(Bool())
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val interrupt_flag = Input(UInt(Parameters.InterruptFlagWidth))
+
+    val output_instruction = Output(UInt(Parameters.DataWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_interrupt_flag = Output(UInt(Parameters.InterruptFlagWidth))
+  })
+
+  val instruction = Module(new PipelineRegister(defaultValue = InstructionsNop.nop))
+  instruction.io.in := io.instruction
+  instruction.io.stall := io.stall
+  instruction.io.flush := io.flush
+  io.output_instruction := instruction.io.out
+
+  val instruction_address = Module(new PipelineRegister(defaultValue = ProgramCounter.EntryAddress))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := io.stall
+  instruction_address.io.flush := io.flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val interrupt_flag = Module(new PipelineRegister(Parameters.InterruptFlagBits))
+  interrupt_flag.io.in := io.interrupt_flag
+  interrupt_flag.io.stall := io.stall
+  interrupt_flag.io.flush := io.flush
+  io.output_interrupt_flag := interrupt_flag.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_forward/InstructionDecode.scala

@@ -0,0 +1,207 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+object InstructionTypes {
+  val L = "b0000011".U
+  val I = "b0010011".U
+  val S = "b0100011".U
+  val RM = "b0110011".U
+  val B = "b1100011".U
+}
+
+object Instructions {
+  val lui = "b0110111".U
+  val nop = "b0000001".U
+  val jal = "b1101111".U
+  val jalr = "b1100111".U
+  val auipc = "b0010111".U
+  val csr = "b1110011".U
+  val fence = "b0001111".U
+}
+
+object InstructionsTypeL {
+  val lb = "b000".U
+  val lh = "b001".U
+  val lw = "b010".U
+  val lbu = "b100".U
+  val lhu = "b101".U
+}
+
+object InstructionsTypeI {
+  val addi = 0.U
+  val slli = 1.U
+  val slti = 2.U
+  val sltiu = 3.U
+  val xori = 4.U
+  val sri = 5.U
+  val ori = 6.U
+  val andi = 7.U
+}
+
+object InstructionsTypeS {
+  val sb = "b000".U
+  val sh = "b001".U
+  val sw = "b010".U
+}
+
+object InstructionsTypeR {
+  val add_sub = 0.U
+  val sll = 1.U
+  val slt = 2.U
+  val sltu = 3.U
+  val xor = 4.U
+  val sr = 5.U
+  val or = 6.U
+  val and = 7.U
+}
+
+object InstructionsTypeM {
+  val mul = 0.U
+  val mulh = 1.U
+  val mulhsu = 2.U
+  val mulhum = 3.U
+  val div = 4.U
+  val divu = 5.U
+  val rem = 6.U
+  val remu = 7.U
+}
+
+object InstructionsTypeB {
+  val beq = "b000".U
+  val bne = "b001".U
+  val blt = "b100".U
+  val bge = "b101".U
+  val bltu = "b110".U
+  val bgeu = "b111".U
+}
+
+object InstructionsTypeCSR {
+  val csrrw = "b001".U
+  val csrrs = "b010".U
+  val csrrc = "b011".U
+  val csrrwi = "b101".U
+  val csrrsi = "b110".U
+  val csrrci = "b111".U
+}
+
+object InstructionsNop {
+  val nop = 0x00000013L.U(Parameters.DataWidth)
+}
+
+object InstructionsRet {
+  val mret = 0x30200073L.U(Parameters.DataWidth)
+  val ret = 0x00008067L.U(Parameters.DataWidth)
+}
+
+object InstructionsEnv {
+  val ecall = 0x00000073L.U(Parameters.DataWidth)
+  val ebreak = 0x00100073L.U(Parameters.DataWidth)
+}
+
+object ALUOp1Source {
+  val Register = 0.U(1.W)
+  val InstructionAddress = 1.U(1.W)
+}
+
+object ALUOp2Source {
+  val Register = 0.U(1.W)
+  val Immediate = 1.U(1.W)
+}
+
+object RegWriteSource {
+  val ALUResult = 0.U(2.W)
+  val Memory = 1.U(2.W)
+  val CSR = 2.U(2.W)
+  val NextInstructionAddress = 3.U(2.W)
+}
+
+class InstructionDecode extends Module {
+  val io = IO(new Bundle {
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+
+    val regs_reg1_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_reg2_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val ex_immediate = Output(UInt(Parameters.DataWidth))
+    val ex_aluop1_source = Output(Bool())
+    val ex_aluop2_source = Output(Bool())
+    val ex_memory_read_enable = Output(Bool())
+    val ex_memory_write_enable = Output(Bool())
+    val ex_reg_write_source = Output(UInt(2.W))
+    val ex_reg_write_enable = Output(Bool())
+    val ex_reg_write_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val ex_csr_address = Output(UInt(Parameters.CSRRegisterAddrWidth))
+    val ex_csr_write_enable = Output(Bool())
+  })
+  val opcode = io.instruction(6, 0)
+  val funct3 = io.instruction(14, 12)
+  val funct7 = io.instruction(31, 25)
+  val rd = io.instruction(11, 7)
+  val rs1 = io.instruction(19, 15)
+  val rs2 = io.instruction(24, 20)
+
+  io.regs_reg1_read_address := Mux(opcode === Instructions.lui, 0.U(Parameters.PhysicalRegisterAddrWidth), rs1)
+  io.regs_reg2_read_address := rs2
+  io.ex_immediate := MuxLookup(
+    opcode,
+    Cat(Fill(20, io.instruction(31)), io.instruction(31, 20)),
+    IndexedSeq(
+      InstructionTypes.I -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      InstructionTypes.L -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      Instructions.jalr -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      InstructionTypes.S -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 25), io.instruction(11, 7)),
+      InstructionTypes.B -> Cat(Fill(20, io.instruction(31)), io.instruction(7), io.instruction(30, 25), io.instruction(11, 8), 0.U(1.W)),
+      Instructions.lui -> Cat(io.instruction(31, 12), 0.U(12.W)),
+      Instructions.auipc -> Cat(io.instruction(31, 12), 0.U(12.W)),
+      Instructions.jal -> Cat(Fill(12, io.instruction(31)), io.instruction(19, 12), io.instruction(20), io.instruction(30, 21), 0.U(1.W))
+    )
+  )
+  io.ex_aluop1_source := Mux(
+    opcode === Instructions.auipc || opcode === InstructionTypes.B || opcode === Instructions.jal,
+    ALUOp1Source.InstructionAddress,
+    ALUOp1Source.Register
+  )
+  io.ex_aluop2_source := Mux(
+    opcode === InstructionTypes.RM,
+    ALUOp2Source.Register,
+    ALUOp2Source.Immediate
+  )
+  io.ex_memory_read_enable := opcode === InstructionTypes.L
+  io.ex_memory_write_enable := opcode === InstructionTypes.S
+  io.ex_reg_write_source := MuxLookup(
+    opcode,
+    RegWriteSource.ALUResult,
+    IndexedSeq(
+      InstructionTypes.L -> RegWriteSource.Memory,
+      Instructions.csr -> RegWriteSource.CSR,
+      Instructions.jal -> RegWriteSource.NextInstructionAddress,
+      Instructions.jalr -> RegWriteSource.NextInstructionAddress
+    )
+  )
+  io.ex_reg_write_enable := (opcode === InstructionTypes.RM) || (opcode === InstructionTypes.I) ||
+    (opcode === InstructionTypes.L) || (opcode === Instructions.auipc) || (opcode === Instructions.lui) ||
+    (opcode === Instructions.jal) || (opcode === Instructions.jalr) || (opcode === Instructions.csr)
+  io.ex_reg_write_address := io.instruction(11, 7)
+  io.ex_csr_address := io.instruction(31, 20)
+  io.ex_csr_write_enable := (opcode === Instructions.csr) && (
+    funct3 === InstructionsTypeCSR.csrrw || funct3 === InstructionsTypeCSR.csrrwi ||
+      funct3 === InstructionsTypeCSR.csrrs || funct3 === InstructionsTypeCSR.csrrsi ||
+      funct3 === InstructionsTypeCSR.csrrc || funct3 === InstructionsTypeCSR.csrrci
+    )
+}

lab3/src/main/scala/riscv/core/fivestage_forward/InstructionFetch.scala

@@ -0,0 +1,48 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import chisel3.util.MuxCase
+import riscv.Parameters
+
+object ProgramCounter {
+  val EntryAddress = Parameters.EntryAddress
+}
+
+class InstructionFetch extends Module {
+  val io = IO(new Bundle {
+    val stall_flag_ctrl = Input(Bool())
+    val jump_flag_id = Input(Bool())
+    val jump_address_id = Input(UInt(Parameters.AddrWidth))
+    val rom_instruction = Input(UInt(Parameters.DataWidth))
+    val instruction_valid = Input(Bool())
+
+    val instruction_address = Output(UInt(Parameters.AddrWidth))
+    val id_instruction = Output(UInt(Parameters.InstructionWidth))
+  })
+  val pc = RegInit(ProgramCounter.EntryAddress)
+
+  pc := MuxCase(
+    pc + 4.U,
+    IndexedSeq(
+      (io.jump_flag_id && !io.stall_flag_ctrl) -> io.jump_address_id,
+      (io.stall_flag_ctrl || !io.instruction_valid) -> pc
+    )
+  )
+
+  io.instruction_address := pc
+  io.id_instruction := Mux(io.instruction_valid, io.rom_instruction, InstructionsNop.nop)
+}

lab3/src/main/scala/riscv/core/fivestage_forward/MEM2WB.scala

@@ -0,0 +1,83 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class MEM2WB extends Module {
+  val io = IO(new Bundle() {
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val regs_write_enable = Input(Bool())
+    val regs_write_source = Input(UInt(2.W))
+    val regs_write_address = Input(UInt(Parameters.AddrWidth))
+    val memory_read_data = Input(UInt(Parameters.DataWidth))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_alu_result = Output(UInt(Parameters.DataWidth))
+    val output_regs_write_enable = Output(Bool())
+    val output_regs_write_source = Output(UInt(2.W))
+    val output_regs_write_address = Output(UInt(Parameters.AddrWidth))
+    val output_memory_read_data = Output(UInt(Parameters.DataWidth))
+    val output_csr_read_data = Output(UInt(Parameters.DataWidth))
+  })
+  val stall = false.B
+  val flush = false.B
+
+  val alu_result = Module(new PipelineRegister())
+  alu_result.io.in := io.alu_result
+  alu_result.io.stall := stall
+  alu_result.io.flush := flush
+  io.output_alu_result := alu_result.io.out
+
+  val memory_read_data = Module(new PipelineRegister())
+  memory_read_data.io.in := io.memory_read_data
+  memory_read_data.io.stall := stall
+  memory_read_data.io.flush := flush
+  io.output_memory_read_data := memory_read_data.io.out
+
+  val regs_write_enable = Module(new PipelineRegister(1))
+  regs_write_enable.io.in := io.regs_write_enable
+  regs_write_enable.io.stall := stall
+  regs_write_enable.io.flush := flush
+  io.output_regs_write_enable := regs_write_enable.io.out
+
+  val regs_write_source = Module(new PipelineRegister(2))
+  regs_write_source.io.in := io.regs_write_source
+  regs_write_source.io.stall := stall
+  regs_write_source.io.flush := flush
+  io.output_regs_write_source := regs_write_source.io.out
+
+  val regs_write_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_write_address.io.in := io.regs_write_address
+  regs_write_address.io.stall := stall
+  regs_write_address.io.flush := flush
+  io.output_regs_write_address := regs_write_address.io.out
+
+  val instruction_address = Module(new PipelineRegister(Parameters.InstructionBits))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val csr_read_data = Module(new PipelineRegister())
+  csr_read_data.io.in := io.csr_read_data
+  csr_read_data.io.stall := stall
+  csr_read_data.io.flush := flush
+  io.output_csr_read_data := csr_read_data.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_forward/MemoryAccess.scala

@@ -0,0 +1,109 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import chisel3.util._
+import peripheral.RAMBundle
+import riscv.Parameters
+
+class MemoryAccess extends Module {
+  val io = IO(new Bundle() {
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val memory_read_enable = Input(Bool())
+    val memory_write_enable = Input(Bool())
+    val funct3 = Input(UInt(3.W))
+    val regs_write_source = Input(UInt(2.W))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val wb_memory_read_data = Output(UInt(Parameters.DataWidth))
+    val forward_data = Output(UInt(Parameters.DataWidth))
+
+    val bundle = Flipped(new RAMBundle)
+  })
+  val mem_address_index = io.alu_result(log2Up(Parameters.WordSize) - 1, 0).asUInt
+
+  io.bundle.write_enable := io.memory_write_enable
+  io.bundle.write_data := 0.U
+  io.bundle.address := io.alu_result
+  io.bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(false.B))
+  io.wb_memory_read_data := 0.U
+
+  when(io.memory_read_enable) {
+    val data = io.bundle.read_data
+    io.wb_memory_read_data := MuxLookup(
+      io.funct3,
+      0.U,
+      IndexedSeq(
+        InstructionsTypeL.lb -> MuxLookup(
+          mem_address_index,
+          Cat(Fill(24, data(31)), data(31, 24)),
+          IndexedSeq(
+            0.U -> Cat(Fill(24, data(7)), data(7, 0)),
+            1.U -> Cat(Fill(24, data(15)), data(15, 8)),
+            2.U -> Cat(Fill(24, data(23)), data(23, 16))
+          )
+        ),
+        InstructionsTypeL.lbu -> MuxLookup(
+          mem_address_index,
+          Cat(Fill(24, 0.U), data(31, 24)),
+          IndexedSeq(
+            0.U -> Cat(Fill(24, 0.U), data(7, 0)),
+            1.U -> Cat(Fill(24, 0.U), data(15, 8)),
+            2.U -> Cat(Fill(24, 0.U), data(23, 16))
+          )
+        ),
+        InstructionsTypeL.lh -> Mux(
+          mem_address_index === 0.U,
+          Cat(Fill(16, data(15)), data(15, 0)),
+          Cat(Fill(16, data(31)), data(31, 16))
+        ),
+        InstructionsTypeL.lhu -> Mux(
+          mem_address_index === 0.U,
+          Cat(Fill(16, 0.U), data(15, 0)),
+          Cat(Fill(16, 0.U), data(31, 16))
+        ),
+        InstructionsTypeL.lw -> data
+      )
+    )
+  }.elsewhen(io.memory_write_enable) {
+    io.bundle.write_data := io.reg2_data
+    io.bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(false.B))
+    when(io.funct3 === InstructionsTypeS.sb) {
+      io.bundle.write_strobe(mem_address_index) := true.B
+      io.bundle.write_data := io.reg2_data(Parameters.ByteBits, 0) << (mem_address_index << log2Up(Parameters.ByteBits).U)
+    }.elsewhen(io.funct3 === InstructionsTypeS.sh) {
+      when(mem_address_index === 0.U) {
+        for (i <- 0 until Parameters.WordSize / 2) {
+          io.bundle.write_strobe(i) := true.B
+        }
+        io.bundle.write_data := io.reg2_data(Parameters.WordSize / 2 * Parameters.ByteBits, 0)
+      }.otherwise {
+        for (i <- Parameters.WordSize / 2 until Parameters.WordSize) {
+          io.bundle.write_strobe(i) := true.B
+        }
+        io.bundle.write_data := io.reg2_data(Parameters.WordSize / 2 * Parameters.ByteBits, 0) << (Parameters
+          .WordSize / 2 * Parameters.ByteBits)
+      }
+    }.elsewhen(io.funct3 === InstructionsTypeS.sw) {
+      for (i <- 0 until Parameters.WordSize) {
+        io.bundle.write_strobe(i) := true.B
+      }
+    }
+  }
+
+  io.forward_data := Mux(io.regs_write_source === RegWriteSource.CSR, io.csr_read_data, io.alu_result)
+}

lab3/src/main/scala/riscv/core/fivestage_forward/WriteBack.scala

@@ -0,0 +1,40 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_forward
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+class WriteBack extends Module {
+  val io = IO(new Bundle() {
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val memory_read_data = Input(UInt(Parameters.DataWidth))
+    val regs_write_source = Input(UInt(2.W))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val regs_write_data = Output(UInt(Parameters.DataWidth))
+  })
+  io.regs_write_data := MuxLookup(
+    io.regs_write_source,
+    io.alu_result,
+    IndexedSeq(
+      RegWriteSource.Memory -> io.memory_read_data,
+      RegWriteSource.CSR -> io.csr_read_data,
+      RegWriteSource.NextInstructionAddress -> (io.instruction_address + 4.U)
+    )
+  )
+}

lab3/src/main/scala/riscv/core/fivestage_stall/CLINT.scala

@@ -0,0 +1,103 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import chisel3.util.MuxLookup
+import riscv.Parameters
+
+object InterruptStatus {
+  val None = 0x0.U(8.W)
+  val Timer0 = 0x1.U(8.W)
+  val Ret = 0xFF.U(8.W)
+}
+
+class CSRDirectAccessBundle extends Bundle {
+  val mstatus = Input(UInt(Parameters.DataWidth))
+  val mepc = Input(UInt(Parameters.DataWidth))
+  val mcause = Input(UInt(Parameters.DataWidth))
+  val mtvec = Input(UInt(Parameters.DataWidth))
+
+  val mstatus_write_data = Output(UInt(Parameters.DataWidth))
+  val mepc_write_data = Output(UInt(Parameters.DataWidth))
+  val mcause_write_data = Output(UInt(Parameters.DataWidth))
+
+  val direct_write_enable = Output(Bool())
+}
+
+// Core Local Interrupt Controller
+class CLINT extends Module {
+  val io = IO(new Bundle {
+    val interrupt_flag = Input(UInt(Parameters.InterruptFlagWidth))
+
+    val instruction_ex = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address_if = Input(UInt(Parameters.AddrWidth))
+    val instruction_address_id = Input(UInt(Parameters.AddrWidth))
+
+    val jump_flag = Input(Bool())
+    val jump_address = Input(UInt(Parameters.AddrWidth))
+
+    val ex_interrupt_handler_address = Output(UInt(Parameters.AddrWidth))
+    val ex_interrupt_assert = Output(Bool())
+
+    val csr_bundle = new CSRDirectAccessBundle
+  })
+  val interrupt_enable = io.csr_bundle.mstatus(3)
+  val jumpping = RegNext(io.jump_flag || io.ex_interrupt_assert)
+  val instruction_address = Mux(
+    io.jump_flag,
+    io.jump_address,
+    Mux(jumpping, io.instruction_address_if, io.instruction_address_id)
+  )
+  val mstatus_disable_interrupt = io.csr_bundle.mstatus(31, 4) ## 0.U(1.W) ## io.csr_bundle.mstatus(2, 0)
+  val mstatus_recover_interrupt = io.csr_bundle.mstatus(31, 4) ## io.csr_bundle.mstatus(7) ## io.csr_bundle.mstatus(2, 0)
+
+  when(io.instruction_ex === InstructionsEnv.ecall || io.instruction_ex === InstructionsEnv.ebreak) {
+    io.csr_bundle.mstatus_write_data := mstatus_disable_interrupt
+    io.csr_bundle.mepc_write_data := instruction_address
+    io.csr_bundle.mcause_write_data := MuxLookup(
+      io.instruction_ex,
+      10.U,
+      IndexedSeq(
+        InstructionsEnv.ecall -> 11.U,
+        InstructionsEnv.ebreak -> 3.U,
+      )
+    )
+    io.csr_bundle.direct_write_enable := true.B
+    io.ex_interrupt_assert := true.B
+    io.ex_interrupt_handler_address := io.csr_bundle.mtvec
+  }.elsewhen(io.interrupt_flag =/= InterruptStatus.None && interrupt_enable) {
+    io.csr_bundle.mstatus_write_data := mstatus_disable_interrupt
+    io.csr_bundle.mepc_write_data := instruction_address
+    io.csr_bundle.mcause_write_data := Mux(io.interrupt_flag(0), 0x80000007L.U, 0x8000000BL.U)
+    io.csr_bundle.direct_write_enable := true.B
+    io.ex_interrupt_assert := true.B
+    io.ex_interrupt_handler_address := io.csr_bundle.mtvec
+  }.elsewhen(io.instruction_ex === InstructionsRet.mret) {
+    io.csr_bundle.mstatus_write_data := mstatus_recover_interrupt
+    io.csr_bundle.mepc_write_data := io.csr_bundle.mepc
+    io.csr_bundle.mcause_write_data := io.csr_bundle.mcause
+    io.csr_bundle.direct_write_enable := true.B
+    io.ex_interrupt_assert := true.B
+    io.ex_interrupt_handler_address := io.csr_bundle.mepc
+  }.otherwise {
+    io.csr_bundle.mstatus_write_data := io.csr_bundle.mstatus
+    io.csr_bundle.mepc_write_data := io.csr_bundle.mepc
+    io.csr_bundle.mcause_write_data := io.csr_bundle.mcause
+    io.csr_bundle.direct_write_enable := false.B
+    io.ex_interrupt_assert := false.B
+    io.ex_interrupt_handler_address := 0.U
+  }
+}

lab3/src/main/scala/riscv/core/fivestage_stall/CPU.scala

@@ -0,0 +1,148 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.{CPUBundle, CSR, RegisterFile}
+
+class CPU extends Module {
+  val io = IO(new CPUBundle)
+
+  val ctrl = Module(new Control)
+  val regs = Module(new RegisterFile)
+  val inst_fetch = Module(new InstructionFetch)
+  val if2id = Module(new IF2ID)
+  val id = Module(new InstructionDecode)
+  val id2ex = Module(new ID2EX)
+  val ex = Module(new Execute)
+  val ex2mem = Module(new EX2MEM)
+  val mem = Module(new MemoryAccess)
+  val mem2wb = Module(new MEM2WB)
+  val wb = Module(new WriteBack)
+  val clint = Module(new CLINT)
+  val csr_regs = Module(new CSR)
+
+  ctrl.io.jump_flag := ex.io.if_jump_flag
+  ctrl.io.rs1_id := id.io.regs_reg1_read_address
+  ctrl.io.rs2_id := id.io.regs_reg2_read_address
+  ctrl.io.rd_ex := id2ex.io.output_regs_write_address
+  ctrl.io.reg_write_enable_ex := id2ex.io.output_regs_write_enable
+  ctrl.io.rd_mem := ex2mem.io.output_regs_write_address
+  ctrl.io.reg_write_enable_mem := ex2mem.io.output_regs_write_enable
+
+  regs.io.write_enable := mem2wb.io.output_regs_write_enable
+  regs.io.write_address := mem2wb.io.output_regs_write_address
+  regs.io.write_data := wb.io.regs_write_data
+  regs.io.read_address1 := id.io.regs_reg1_read_address
+  regs.io.read_address2 := id.io.regs_reg2_read_address
+
+  regs.io.debug_read_address := io.debug_read_address
+  io.debug_read_data := regs.io.debug_read_data
+
+  io.instruction_address := inst_fetch.io.instruction_address
+  inst_fetch.io.stall_flag_ctrl := ctrl.io.pc_stall
+  inst_fetch.io.jump_flag_id := ex.io.if_jump_flag
+  inst_fetch.io.jump_address_id := ex.io.if_jump_address
+  inst_fetch.io.rom_instruction := io.instruction
+  inst_fetch.io.instruction_valid := io.instruction_valid
+
+  if2id.io.stall := ctrl.io.if_stall
+  if2id.io.flush := ctrl.io.if_flush
+  if2id.io.instruction := inst_fetch.io.id_instruction
+  if2id.io.instruction_address := inst_fetch.io.instruction_address
+  if2id.io.interrupt_flag := io.interrupt_flag
+
+  id.io.instruction := if2id.io.output_instruction
+
+  id2ex.io.flush := ctrl.io.id_flush
+  id2ex.io.instruction := if2id.io.output_instruction
+  id2ex.io.instruction_address := if2id.io.output_instruction_address
+  id2ex.io.reg1_data := regs.io.read_data1
+  id2ex.io.reg2_data := regs.io.read_data2
+  id2ex.io.regs_reg1_read_address := id.io.regs_reg1_read_address
+  id2ex.io.regs_reg2_read_address := id.io.regs_reg2_read_address
+  id2ex.io.regs_write_enable := id.io.ex_reg_write_enable
+  id2ex.io.regs_write_address := id.io.ex_reg_write_address
+  id2ex.io.regs_write_source := id.io.ex_reg_write_source
+  id2ex.io.immediate := id.io.ex_immediate
+  id2ex.io.aluop1_source := id.io.ex_aluop1_source
+  id2ex.io.aluop2_source := id.io.ex_aluop2_source
+  id2ex.io.csr_write_enable := id.io.ex_csr_write_enable
+  id2ex.io.csr_address := id.io.ex_csr_address
+  id2ex.io.memory_read_enable := id.io.ex_memory_read_enable
+  id2ex.io.memory_write_enable := id.io.ex_memory_write_enable
+  id2ex.io.csr_read_data := csr_regs.io.id_reg_read_data
+
+  ex.io.instruction := id2ex.io.output_instruction
+  ex.io.instruction_address := id2ex.io.output_instruction_address
+  ex.io.reg1_data := id2ex.io.output_reg1_data
+  ex.io.reg2_data := id2ex.io.output_reg2_data
+  ex.io.immediate_id := id2ex.io.output_immediate
+  ex.io.aluop1_source_id := id2ex.io.output_aluop1_source
+  ex.io.aluop2_source_id := id2ex.io.output_aluop2_source
+  ex.io.csr_read_data_id := id2ex.io.output_csr_read_data
+  ex.io.interrupt_assert_clint := clint.io.ex_interrupt_assert
+  ex.io.interrupt_handler_address_clint := clint.io.ex_interrupt_handler_address
+
+  ex2mem.io.regs_write_enable := id2ex.io.output_regs_write_enable
+  ex2mem.io.regs_write_source := id2ex.io.output_regs_write_source
+  ex2mem.io.regs_write_address := id2ex.io.output_regs_write_address
+  ex2mem.io.instruction_address := id2ex.io.output_instruction_address
+  ex2mem.io.funct3 := id2ex.io.output_instruction(14, 12)
+  ex2mem.io.reg2_data := ex.io.mem_reg2_data
+  ex2mem.io.memory_read_enable := id2ex.io.output_memory_read_enable
+  ex2mem.io.memory_write_enable := id2ex.io.output_memory_write_enable
+  ex2mem.io.alu_result := ex.io.mem_alu_result
+  ex2mem.io.csr_read_data := id2ex.io.output_csr_read_data
+
+  mem.io.alu_result := ex2mem.io.output_alu_result
+  mem.io.reg2_data := ex2mem.io.output_reg2_data
+  mem.io.memory_read_enable := ex2mem.io.output_memory_read_enable
+  mem.io.memory_write_enable := ex2mem.io.output_memory_write_enable
+  mem.io.funct3 := ex2mem.io.output_funct3
+  mem.io.regs_write_source := ex2mem.io.output_regs_write_source
+  mem.io.csr_read_data := ex2mem.io.output_csr_read_data
+  io.device_select := mem.io.bundle.address(Parameters.AddrBits - 1, Parameters.AddrBits - Parameters.SlaveDeviceCountBits)
+  io.memory_bundle <> mem.io.bundle
+  io.memory_bundle.address := 0.U(Parameters.SlaveDeviceCountBits.W) ## mem.io.bundle.address(Parameters.AddrBits - 1 - Parameters.SlaveDeviceCountBits, 0)
+
+  mem2wb.io.instruction_address := ex2mem.io.output_instruction_address
+  mem2wb.io.alu_result := ex2mem.io.output_alu_result
+  mem2wb.io.regs_write_enable := ex2mem.io.output_regs_write_enable
+  mem2wb.io.regs_write_source := ex2mem.io.output_regs_write_source
+  mem2wb.io.regs_write_address := ex2mem.io.output_regs_write_address
+  mem2wb.io.memory_read_data := mem.io.wb_memory_read_data
+  mem2wb.io.csr_read_data := ex2mem.io.output_csr_read_data
+
+  wb.io.instruction_address := mem2wb.io.output_instruction_address
+  wb.io.alu_result := mem2wb.io.output_alu_result
+  wb.io.memory_read_data := mem2wb.io.output_memory_read_data
+  wb.io.regs_write_source := mem2wb.io.output_regs_write_source
+  wb.io.csr_read_data := mem2wb.io.output_csr_read_data
+
+  clint.io.instruction_address_if := inst_fetch.io.instruction_address
+  clint.io.instruction_address_id := if2id.io.output_instruction_address
+  clint.io.instruction_ex := id2ex.io.output_instruction
+  clint.io.jump_flag := ex.io.clint_jump_flag
+  clint.io.jump_address := ex.io.clint_jump_address
+  clint.io.interrupt_flag := if2id.io.output_interrupt_flag
+  clint.io.csr_bundle <> csr_regs.io.clint_access_bundle
+
+  csr_regs.io.reg_read_address_id := id.io.ex_csr_address
+  csr_regs.io.reg_write_enable_ex := id2ex.io.output_csr_write_enable
+  csr_regs.io.reg_write_address_ex := id2ex.io.output_csr_address
+  csr_regs.io.reg_write_data_ex := ex.io.csr_write_data
+}

lab3/src/main/scala/riscv/core/fivestage_stall/Control.scala

@@ -0,0 +1,43 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import riscv.Parameters
+
+class Control extends Module {
+  val io = IO(new Bundle {
+    val jump_flag = Input(Bool())
+    val rs1_id = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val rs2_id = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val rd_ex = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val reg_write_enable_ex = Input(Bool())
+    val rd_mem = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val reg_write_enable_mem = Input(Bool())
+
+    val if_flush = Output(Bool())
+    val id_flush = Output(Bool())
+    val pc_stall = Output(Bool())
+    val if_stall = Output(Bool())
+  })
+
+  // Lab3(Stall)
+  io.if_flush := false.B
+  io.id_flush := false.B
+
+  io.pc_stall := false.B
+  io.if_stall := false.B
+  // Lab3(Stall) End
+}

lab3/src/main/scala/riscv/core/fivestage_stall/EX2MEM.scala

@@ -0,0 +1,108 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class EX2MEM extends Module {
+  val io = IO(new Bundle() {
+    val regs_write_enable = Input(Bool())
+    val regs_write_source = Input(UInt(2.W))
+    val regs_write_address = Input(UInt(Parameters.AddrWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val funct3 = Input(UInt(3.W))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val memory_read_enable = Input(Bool())
+    val memory_write_enable = Input(Bool())
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val output_regs_write_enable = Output(Bool())
+    val output_regs_write_source = Output(UInt(2.W))
+    val output_regs_write_address = Output(UInt(Parameters.AddrWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_funct3 = Output(UInt(Parameters.DataWidth))
+    val output_reg2_data = Output(UInt(Parameters.DataWidth))
+    val output_memory_read_enable = Output(Bool())
+    val output_memory_write_enable = Output(Bool())
+    val output_alu_result = Output(UInt(Parameters.DataWidth))
+    val output_csr_read_data = Output(UInt(Parameters.DataWidth))
+  })
+
+  val stall = false.B
+  val flush = false.B
+
+  val regs_write_enable = Module(new PipelineRegister(1))
+  regs_write_enable.io.in := io.regs_write_enable
+  regs_write_enable.io.stall := stall
+  regs_write_enable.io.flush := flush
+  io.output_regs_write_enable := regs_write_enable.io.out
+
+  val regs_write_source = Module(new PipelineRegister(2))
+  regs_write_source.io.in := io.regs_write_source
+  regs_write_source.io.stall := stall
+  regs_write_source.io.flush := flush
+  io.output_regs_write_source := regs_write_source.io.out
+
+  val regs_write_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_write_address.io.in := io.regs_write_address
+  regs_write_address.io.stall := stall
+  regs_write_address.io.flush := flush
+  io.output_regs_write_address := regs_write_address.io.out
+
+  val instruction_address = Module(new PipelineRegister(Parameters.AddrBits))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val funct3 = Module(new PipelineRegister(3))
+  funct3.io.in := io.funct3
+  funct3.io.stall := stall
+  funct3.io.flush := flush
+  io.output_funct3 := funct3.io.out
+
+  val reg2_data = Module(new PipelineRegister())
+  reg2_data.io.in := io.reg2_data
+  reg2_data.io.stall := stall
+  reg2_data.io.flush := flush
+  io.output_reg2_data := reg2_data.io.out
+
+  val alu_result = Module(new PipelineRegister())
+  alu_result.io.in := io.alu_result
+  alu_result.io.stall := stall
+  alu_result.io.flush := flush
+  io.output_alu_result := alu_result.io.out
+
+  val memory_read_enable = Module(new PipelineRegister(1))
+  memory_read_enable.io.in := io.memory_read_enable
+  memory_read_enable.io.stall := stall
+  memory_read_enable.io.flush := flush
+  io.output_memory_read_enable := memory_read_enable.io.out
+
+  val memory_write_enable = Module(new PipelineRegister(1))
+  memory_write_enable.io.in := io.memory_write_enable
+  memory_write_enable.io.stall := stall
+  memory_write_enable.io.flush := flush
+  io.output_memory_write_enable := memory_write_enable.io.out
+
+  val csr_read_data = Module(new PipelineRegister())
+  csr_read_data.io.in := io.csr_read_data
+  csr_read_data.io.stall := stall
+  csr_read_data.io.flush := flush
+  io.output_csr_read_data := csr_read_data.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_stall/Execute.scala

@@ -0,0 +1,101 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+import riscv.core.{ALU, ALUControl}
+
+
+class Execute extends Module {
+  val io = IO(new Bundle {
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val reg1_data = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val immediate_id = Input(UInt(Parameters.DataWidth))
+    val aluop1_source_id = Input(UInt(1.W))
+    val aluop2_source_id = Input(UInt(1.W))
+    val csr_read_data_id = Input(UInt(Parameters.DataWidth))
+    val interrupt_assert_clint = Input(Bool())
+    val interrupt_handler_address_clint = Input(UInt(Parameters.AddrWidth))
+
+    val mem_alu_result = Output(UInt(Parameters.DataWidth))
+    val mem_reg2_data = Output(UInt(Parameters.DataWidth))
+    val csr_write_data = Output(UInt(Parameters.DataWidth))
+    val if_jump_flag = Output(Bool())
+    val if_jump_address = Output(UInt(Parameters.AddrWidth))
+    val clint_jump_flag = Output(Bool())
+    val clint_jump_address = Output(UInt(Parameters.AddrWidth))
+  })
+
+  val opcode = io.instruction(6, 0)
+  val funct3 = io.instruction(14, 12)
+  val funct7 = io.instruction(31, 25)
+  val uimm = io.instruction(19, 15)
+
+  // ALU compute
+  val alu = Module(new ALU)
+  val alu_ctrl = Module(new ALUControl)
+
+  alu_ctrl.io.opcode := opcode
+  alu_ctrl.io.funct3 := funct3
+  alu_ctrl.io.funct7 := funct7
+  alu.io.func := alu_ctrl.io.alu_funct
+  alu.io.op1 := Mux(
+    io.aluop1_source_id === ALUOp1Source.InstructionAddress,
+    io.instruction_address,
+    io.reg1_data
+  )
+  alu.io.op2 := Mux(
+    io.aluop2_source_id === ALUOp2Source.Immediate,
+    io.immediate_id,
+    io.reg2_data
+  )
+  io.mem_alu_result := alu.io.result
+  io.mem_reg2_data := io.reg2_data
+  io.csr_write_data := MuxLookup(funct3, 0.U, IndexedSeq(
+    InstructionsTypeCSR.csrrw -> io.reg1_data,
+    InstructionsTypeCSR.csrrc -> io.csr_read_data_id.&((~io.reg1_data).asUInt),
+    InstructionsTypeCSR.csrrs -> io.csr_read_data_id.|(io.reg1_data),
+    InstructionsTypeCSR.csrrwi -> Cat(0.U(27.W), uimm),
+    InstructionsTypeCSR.csrrci -> io.csr_read_data_id.&((~Cat(0.U(27.W), uimm)).asUInt),
+    InstructionsTypeCSR.csrrsi -> io.csr_read_data_id.|(Cat(0.U(27.W), uimm)),
+  ))
+
+  // jump and interrupt
+  val instruction_jump_flag = (opcode === Instructions.jal) ||
+    (opcode === Instructions.jalr) ||
+    (opcode === InstructionTypes.B) && MuxLookup(
+      funct3,
+      false.B,
+      IndexedSeq(
+        InstructionsTypeB.beq -> (io.reg1_data === io.reg2_data),
+        InstructionsTypeB.bne -> (io.reg1_data =/= io.reg2_data),
+        InstructionsTypeB.blt -> (io.reg1_data.asSInt < io.reg2_data.asSInt),
+        InstructionsTypeB.bge -> (io.reg1_data.asSInt >= io.reg2_data.asSInt),
+        InstructionsTypeB.bltu -> (io.reg1_data.asUInt < io.reg2_data.asUInt),
+        InstructionsTypeB.bgeu -> (io.reg1_data.asUInt >= io.reg2_data.asUInt)
+      )
+    )
+  io.clint_jump_flag := instruction_jump_flag
+  io.clint_jump_address := alu.io.result
+  io.if_jump_flag := io.interrupt_assert_clint || instruction_jump_flag
+  io.if_jump_address := Mux(io.interrupt_assert_clint,
+    io.interrupt_handler_address_clint,
+    alu.io.result
+  )
+}

lab3/src/main/scala/riscv/core/fivestage_stall/ID2EX.scala

@@ -0,0 +1,164 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class ID2EX extends Module {
+  val io = IO(new Bundle {
+    val flush = Input(Bool())
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val regs_reg1_read_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_reg2_read_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_write_enable = Input(Bool())
+    val regs_write_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_write_source = Input(UInt(2.W))
+    val reg1_data = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val immediate = Input(UInt(Parameters.DataWidth))
+    val aluop1_source = Input(UInt(1.W))
+    val aluop2_source = Input(UInt(1.W))
+    val csr_write_enable = Input(Bool())
+    val csr_address = Input(UInt(Parameters.CSRRegisterAddrWidth))
+    val memory_read_enable = Input(Bool())
+    val memory_write_enable = Input(Bool())
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val output_instruction = Output(UInt(Parameters.DataWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_regs_reg1_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val output_regs_reg2_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val output_regs_write_enable = Output(Bool())
+    val output_regs_write_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val output_regs_write_source = Output(UInt(2.W))
+    val output_reg1_data = Output(UInt(Parameters.DataWidth))
+    val output_reg2_data = Output(UInt(Parameters.DataWidth))
+    val output_immediate = Output(UInt(Parameters.DataWidth))
+    val output_aluop1_source = Output(UInt(1.W))
+    val output_aluop2_source = Output(UInt(1.W))
+    val output_csr_write_enable = Output(Bool())
+    val output_csr_address = Output(UInt(Parameters.CSRRegisterAddrWidth))
+    val output_memory_read_enable = Output(Bool())
+    val output_memory_write_enable = Output(Bool())
+    val output_csr_read_data = Output(UInt(Parameters.DataWidth))
+  })
+
+  val stall = false.B
+
+  val instruction = Module(new PipelineRegister(defaultValue = InstructionsNop.nop))
+  instruction.io.in := io.instruction
+  instruction.io.stall := stall
+  instruction.io.flush := io.flush
+  io.output_instruction := instruction.io.out
+
+  val instruction_address = Module(new PipelineRegister(defaultValue = ProgramCounter.EntryAddress))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := io.flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val regs_reg1_read_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_reg1_read_address.io.in := io.regs_reg1_read_address
+  regs_reg1_read_address.io.stall := stall
+  regs_reg1_read_address.io.flush := io.flush
+  io.output_regs_reg1_read_address := regs_reg1_read_address.io.out
+
+  val regs_reg2_read_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_reg2_read_address.io.in := io.regs_reg2_read_address
+  regs_reg2_read_address.io.stall := stall
+  regs_reg2_read_address.io.flush := io.flush
+  io.output_regs_reg2_read_address := regs_reg2_read_address.io.out
+
+  val regs_write_enable = Module(new PipelineRegister(1))
+  regs_write_enable.io.in := io.regs_write_enable
+  regs_write_enable.io.stall := stall
+  regs_write_enable.io.flush := io.flush
+  io.output_regs_write_enable := regs_write_enable.io.out
+
+  val regs_write_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_write_address.io.in := io.regs_write_address
+  regs_write_address.io.stall := stall
+  regs_write_address.io.flush := io.flush
+  io.output_regs_write_address := regs_write_address.io.out
+
+  val regs_write_source = Module(new PipelineRegister(2))
+  regs_write_source.io.in := io.regs_write_source
+  regs_write_source.io.stall := stall
+  regs_write_source.io.flush := io.flush
+  io.output_regs_write_source := regs_write_source.io.out
+
+  val reg1_data = Module(new PipelineRegister())
+  reg1_data.io.in := io.reg1_data
+  reg1_data.io.stall := stall
+  reg1_data.io.flush := io.flush
+  io.output_reg1_data := reg1_data.io.out
+
+  val reg2_data = Module(new PipelineRegister())
+  reg2_data.io.in := io.reg2_data
+  reg2_data.io.stall := stall
+  reg2_data.io.flush := io.flush
+  io.output_reg2_data := reg2_data.io.out
+
+  val immediate = Module(new PipelineRegister())
+  immediate.io.in := io.immediate
+  immediate.io.stall := stall
+  immediate.io.flush := io.flush
+  io.output_immediate := immediate.io.out
+
+  val aluop1_source = Module(new PipelineRegister(1))
+  aluop1_source.io.in := io.aluop1_source
+  aluop1_source.io.stall := stall
+  aluop1_source.io.flush := io.flush
+  io.output_aluop1_source := aluop1_source.io.out
+
+  val aluop2_source = Module(new PipelineRegister(1))
+  aluop2_source.io.in := io.aluop2_source
+  aluop2_source.io.stall := stall
+  aluop2_source.io.flush := io.flush
+  io.output_aluop2_source := aluop2_source.io.out
+
+  val csr_write_enable = Module(new PipelineRegister(1))
+  csr_write_enable.io.in := io.csr_write_enable
+  csr_write_enable.io.stall := stall
+  csr_write_enable.io.flush := io.flush
+  io.output_csr_write_enable := csr_write_enable.io.out
+
+  val csr_address = Module(new PipelineRegister(Parameters.CSRRegisterAddrBits))
+  csr_address.io.in := io.csr_address
+  csr_address.io.stall := stall
+  csr_address.io.flush := io.flush
+  io.output_csr_address := csr_address.io.out
+
+  val memory_read_enable = Module(new PipelineRegister(1))
+  memory_read_enable.io.in := io.memory_read_enable
+  memory_read_enable.io.stall := stall
+  memory_read_enable.io.flush := io.flush
+  io.output_memory_read_enable := memory_read_enable.io.out
+
+  val memory_write_enable = Module(new PipelineRegister(1))
+  memory_write_enable.io.in := io.memory_write_enable
+  memory_write_enable.io.stall := stall
+  memory_write_enable.io.flush := io.flush
+  io.output_memory_write_enable := memory_write_enable.io.out
+
+  val csr_read_data = Module(new PipelineRegister())
+  csr_read_data.io.in := io.csr_read_data
+  csr_read_data.io.stall := stall
+  csr_read_data.io.flush := io.flush
+  io.output_csr_read_data := csr_read_data.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_stall/IF2ID.scala

@@ -0,0 +1,51 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class IF2ID extends Module {
+  val io = IO(new Bundle {
+    val stall = Input(Bool())
+    val flush = Input(Bool())
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val interrupt_flag = Input(UInt(Parameters.InterruptFlagWidth))
+
+    val output_instruction = Output(UInt(Parameters.DataWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_interrupt_flag = Output(UInt(Parameters.InterruptFlagWidth))
+  })
+
+  val instruction = Module(new PipelineRegister(defaultValue = InstructionsNop.nop))
+  instruction.io.in := io.instruction
+  instruction.io.stall := io.stall
+  instruction.io.flush := io.flush
+  io.output_instruction := instruction.io.out
+
+  val instruction_address = Module(new PipelineRegister(defaultValue = ProgramCounter.EntryAddress))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := io.stall
+  instruction_address.io.flush := io.flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val interrupt_flag = Module(new PipelineRegister(Parameters.InterruptFlagBits))
+  interrupt_flag.io.in := io.interrupt_flag
+  interrupt_flag.io.stall := io.stall
+  interrupt_flag.io.flush := io.flush
+  io.output_interrupt_flag := interrupt_flag.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_stall/InstructionDecode.scala

@@ -0,0 +1,207 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+object InstructionTypes {
+  val L = "b0000011".U
+  val I = "b0010011".U
+  val S = "b0100011".U
+  val RM = "b0110011".U
+  val B = "b1100011".U
+}
+
+object Instructions {
+  val lui = "b0110111".U
+  val nop = "b0000001".U
+  val jal = "b1101111".U
+  val jalr = "b1100111".U
+  val auipc = "b0010111".U
+  val csr = "b1110011".U
+  val fence = "b0001111".U
+}
+
+object InstructionsTypeL {
+  val lb = "b000".U
+  val lh = "b001".U
+  val lw = "b010".U
+  val lbu = "b100".U
+  val lhu = "b101".U
+}
+
+object InstructionsTypeI {
+  val addi = 0.U
+  val slli = 1.U
+  val slti = 2.U
+  val sltiu = 3.U
+  val xori = 4.U
+  val sri = 5.U
+  val ori = 6.U
+  val andi = 7.U
+}
+
+object InstructionsTypeS {
+  val sb = "b000".U
+  val sh = "b001".U
+  val sw = "b010".U
+}
+
+object InstructionsTypeR {
+  val add_sub = 0.U
+  val sll = 1.U
+  val slt = 2.U
+  val sltu = 3.U
+  val xor = 4.U
+  val sr = 5.U
+  val or = 6.U
+  val and = 7.U
+}
+
+object InstructionsTypeM {
+  val mul = 0.U
+  val mulh = 1.U
+  val mulhsu = 2.U
+  val mulhum = 3.U
+  val div = 4.U
+  val divu = 5.U
+  val rem = 6.U
+  val remu = 7.U
+}
+
+object InstructionsTypeB {
+  val beq = "b000".U
+  val bne = "b001".U
+  val blt = "b100".U
+  val bge = "b101".U
+  val bltu = "b110".U
+  val bgeu = "b111".U
+}
+
+object InstructionsTypeCSR {
+  val csrrw = "b001".U
+  val csrrs = "b010".U
+  val csrrc = "b011".U
+  val csrrwi = "b101".U
+  val csrrsi = "b110".U
+  val csrrci = "b111".U
+}
+
+object InstructionsNop {
+  val nop = 0x00000013L.U(Parameters.DataWidth)
+}
+
+object InstructionsRet {
+  val mret = 0x30200073L.U(Parameters.DataWidth)
+  val ret = 0x00008067L.U(Parameters.DataWidth)
+}
+
+object InstructionsEnv {
+  val ecall = 0x00000073L.U(Parameters.DataWidth)
+  val ebreak = 0x00100073L.U(Parameters.DataWidth)
+}
+
+object ALUOp1Source {
+  val Register = 0.U(1.W)
+  val InstructionAddress = 1.U(1.W)
+}
+
+object ALUOp2Source {
+  val Register = 0.U(1.W)
+  val Immediate = 1.U(1.W)
+}
+
+object RegWriteSource {
+  val ALUResult = 0.U(2.W)
+  val Memory = 1.U(2.W)
+  val CSR = 2.U(2.W)
+  val NextInstructionAddress = 3.U(2.W)
+}
+
+class InstructionDecode extends Module {
+  val io = IO(new Bundle {
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+
+    val regs_reg1_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_reg2_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val ex_immediate = Output(UInt(Parameters.DataWidth))
+    val ex_aluop1_source = Output(Bool())
+    val ex_aluop2_source = Output(Bool())
+    val ex_memory_read_enable = Output(Bool())
+    val ex_memory_write_enable = Output(Bool())
+    val ex_reg_write_source = Output(UInt(2.W))
+    val ex_reg_write_enable = Output(Bool())
+    val ex_reg_write_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val ex_csr_address = Output(UInt(Parameters.CSRRegisterAddrWidth))
+    val ex_csr_write_enable = Output(Bool())
+  })
+  val opcode = io.instruction(6, 0)
+  val funct3 = io.instruction(14, 12)
+  val funct7 = io.instruction(31, 25)
+  val rd = io.instruction(11, 7)
+  val rs1 = io.instruction(19, 15)
+  val rs2 = io.instruction(24, 20)
+
+  io.regs_reg1_read_address := Mux(opcode === Instructions.lui, 0.U(Parameters.PhysicalRegisterAddrWidth), rs1)
+  io.regs_reg2_read_address := rs2
+  io.ex_immediate := MuxLookup(
+    opcode,
+    Cat(Fill(20, io.instruction(31)), io.instruction(31, 20)),
+    IndexedSeq(
+      InstructionTypes.I -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      InstructionTypes.L -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      Instructions.jalr -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      InstructionTypes.S -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 25), io.instruction(11, 7)),
+      InstructionTypes.B -> Cat(Fill(20, io.instruction(31)), io.instruction(7), io.instruction(30, 25), io.instruction(11, 8), 0.U(1.W)),
+      Instructions.lui -> Cat(io.instruction(31, 12), 0.U(12.W)),
+      Instructions.auipc -> Cat(io.instruction(31, 12), 0.U(12.W)),
+      Instructions.jal -> Cat(Fill(12, io.instruction(31)), io.instruction(19, 12), io.instruction(20), io.instruction(30, 21), 0.U(1.W))
+    )
+  )
+  io.ex_aluop1_source := Mux(
+    opcode === Instructions.auipc || opcode === InstructionTypes.B || opcode === Instructions.jal,
+    ALUOp1Source.InstructionAddress,
+    ALUOp1Source.Register
+  )
+  io.ex_aluop2_source := Mux(
+    opcode === InstructionTypes.RM,
+    ALUOp2Source.Register,
+    ALUOp2Source.Immediate
+  )
+  io.ex_memory_read_enable := opcode === InstructionTypes.L
+  io.ex_memory_write_enable := opcode === InstructionTypes.S
+  io.ex_reg_write_source := MuxLookup(
+    opcode,
+    RegWriteSource.ALUResult,
+    IndexedSeq(
+      InstructionTypes.L -> RegWriteSource.Memory,
+      Instructions.csr -> RegWriteSource.CSR,
+      Instructions.jal -> RegWriteSource.NextInstructionAddress,
+      Instructions.jalr -> RegWriteSource.NextInstructionAddress
+    )
+  )
+  io.ex_reg_write_enable := (opcode === InstructionTypes.RM) || (opcode === InstructionTypes.I) ||
+    (opcode === InstructionTypes.L) || (opcode === Instructions.auipc) || (opcode === Instructions.lui) ||
+    (opcode === Instructions.jal) || (opcode === Instructions.jalr) || (opcode === Instructions.csr)
+  io.ex_reg_write_address := io.instruction(11, 7)
+  io.ex_csr_address := io.instruction(31, 20)
+  io.ex_csr_write_enable := (opcode === Instructions.csr) && (
+    funct3 === InstructionsTypeCSR.csrrw || funct3 === InstructionsTypeCSR.csrrwi ||
+      funct3 === InstructionsTypeCSR.csrrs || funct3 === InstructionsTypeCSR.csrrsi ||
+      funct3 === InstructionsTypeCSR.csrrc || funct3 === InstructionsTypeCSR.csrrci
+    )
+}

lab3/src/main/scala/riscv/core/fivestage_stall/InstructionFetch.scala

@@ -0,0 +1,48 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import chisel3.util.MuxCase
+import riscv.Parameters
+
+object ProgramCounter {
+  val EntryAddress = Parameters.EntryAddress
+}
+
+class InstructionFetch extends Module {
+  val io = IO(new Bundle {
+    val stall_flag_ctrl = Input(Bool())
+    val jump_flag_id = Input(Bool())
+    val jump_address_id = Input(UInt(Parameters.AddrWidth))
+    val rom_instruction = Input(UInt(Parameters.DataWidth))
+    val instruction_valid = Input(Bool())
+
+    val instruction_address = Output(UInt(Parameters.AddrWidth))
+    val id_instruction = Output(UInt(Parameters.InstructionWidth))
+  })
+  val pc = RegInit(ProgramCounter.EntryAddress)
+
+  pc := MuxCase(
+    pc + 4.U,
+    IndexedSeq(
+      (io.jump_flag_id && !io.stall_flag_ctrl) -> io.jump_address_id,
+      (io.stall_flag_ctrl || !io.instruction_valid) -> pc
+    )
+  )
+
+  io.instruction_address := pc
+  io.id_instruction := Mux(io.instruction_valid, io.rom_instruction, InstructionsNop.nop)
+}

lab3/src/main/scala/riscv/core/fivestage_stall/MEM2WB.scala

@@ -0,0 +1,83 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class MEM2WB extends Module {
+  val io = IO(new Bundle() {
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val regs_write_enable = Input(Bool())
+    val regs_write_source = Input(UInt(2.W))
+    val regs_write_address = Input(UInt(Parameters.AddrWidth))
+    val memory_read_data = Input(UInt(Parameters.DataWidth))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_alu_result = Output(UInt(Parameters.DataWidth))
+    val output_regs_write_enable = Output(Bool())
+    val output_regs_write_source = Output(UInt(2.W))
+    val output_regs_write_address = Output(UInt(Parameters.AddrWidth))
+    val output_memory_read_data = Output(UInt(Parameters.DataWidth))
+    val output_csr_read_data = Output(UInt(Parameters.DataWidth))
+  })
+  val stall = false.B
+  val flush = false.B
+
+  val alu_result = Module(new PipelineRegister())
+  alu_result.io.in := io.alu_result
+  alu_result.io.stall := stall
+  alu_result.io.flush := flush
+  io.output_alu_result := alu_result.io.out
+
+  val memory_read_data = Module(new PipelineRegister())
+  memory_read_data.io.in := io.memory_read_data
+  memory_read_data.io.stall := stall
+  memory_read_data.io.flush := flush
+  io.output_memory_read_data := memory_read_data.io.out
+
+  val regs_write_enable = Module(new PipelineRegister(1))
+  regs_write_enable.io.in := io.regs_write_enable
+  regs_write_enable.io.stall := stall
+  regs_write_enable.io.flush := flush
+  io.output_regs_write_enable := regs_write_enable.io.out
+
+  val regs_write_source = Module(new PipelineRegister(2))
+  regs_write_source.io.in := io.regs_write_source
+  regs_write_source.io.stall := stall
+  regs_write_source.io.flush := flush
+  io.output_regs_write_source := regs_write_source.io.out
+
+  val regs_write_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_write_address.io.in := io.regs_write_address
+  regs_write_address.io.stall := stall
+  regs_write_address.io.flush := flush
+  io.output_regs_write_address := regs_write_address.io.out
+
+  val instruction_address = Module(new PipelineRegister(Parameters.InstructionBits))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val csr_read_data = Module(new PipelineRegister())
+  csr_read_data.io.in := io.csr_read_data
+  csr_read_data.io.stall := stall
+  csr_read_data.io.flush := flush
+  io.output_csr_read_data := csr_read_data.io.out
+}

lab3/src/main/scala/riscv/core/fivestage_stall/MemoryAccess.scala

@@ -0,0 +1,106 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import chisel3.util._
+import peripheral.RAMBundle
+import riscv.Parameters
+
+class MemoryAccess extends Module {
+  val io = IO(new Bundle() {
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val memory_read_enable = Input(Bool())
+    val memory_write_enable = Input(Bool())
+    val funct3 = Input(UInt(3.W))
+    val regs_write_source = Input(UInt(2.W))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val wb_memory_read_data = Output(UInt(Parameters.DataWidth))
+
+    val bundle = Flipped(new RAMBundle)
+  })
+  val mem_address_index = io.alu_result(log2Up(Parameters.WordSize) - 1, 0).asUInt
+
+  io.bundle.write_enable := io.memory_write_enable
+  io.bundle.write_data := 0.U
+  io.bundle.address := io.alu_result
+  io.bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(false.B))
+  io.wb_memory_read_data := 0.U
+
+  when(io.memory_read_enable) {
+    val data = io.bundle.read_data
+    io.wb_memory_read_data := MuxLookup(
+      io.funct3,
+      0.U,
+      IndexedSeq(
+        InstructionsTypeL.lb -> MuxLookup(
+          mem_address_index,
+          Cat(Fill(24, data(31)), data(31, 24)),
+          IndexedSeq(
+            0.U -> Cat(Fill(24, data(7)), data(7, 0)),
+            1.U -> Cat(Fill(24, data(15)), data(15, 8)),
+            2.U -> Cat(Fill(24, data(23)), data(23, 16))
+          )
+        ),
+        InstructionsTypeL.lbu -> MuxLookup(
+          mem_address_index,
+          Cat(Fill(24, 0.U), data(31, 24)),
+          IndexedSeq(
+            0.U -> Cat(Fill(24, 0.U), data(7, 0)),
+            1.U -> Cat(Fill(24, 0.U), data(15, 8)),
+            2.U -> Cat(Fill(24, 0.U), data(23, 16))
+          )
+        ),
+        InstructionsTypeL.lh -> Mux(
+          mem_address_index === 0.U,
+          Cat(Fill(16, data(15)), data(15, 0)),
+          Cat(Fill(16, data(31)), data(31, 16))
+        ),
+        InstructionsTypeL.lhu -> Mux(
+          mem_address_index === 0.U,
+          Cat(Fill(16, 0.U), data(15, 0)),
+          Cat(Fill(16, 0.U), data(31, 16))
+        ),
+        InstructionsTypeL.lw -> data
+      )
+    )
+  }.elsewhen(io.memory_write_enable) {
+    io.bundle.write_data := io.reg2_data
+    io.bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(false.B))
+    when(io.funct3 === InstructionsTypeS.sb) {
+      io.bundle.write_strobe(mem_address_index) := true.B
+      io.bundle.write_data := io.reg2_data(Parameters.ByteBits, 0) << (mem_address_index << log2Up(Parameters.ByteBits).U)
+    }.elsewhen(io.funct3 === InstructionsTypeS.sh) {
+      when(mem_address_index === 0.U) {
+        for (i <- 0 until Parameters.WordSize / 2) {
+          io.bundle.write_strobe(i) := true.B
+        }
+        io.bundle.write_data := io.reg2_data(Parameters.WordSize / 2 * Parameters.ByteBits, 0)
+      }.otherwise {
+        for (i <- Parameters.WordSize / 2 until Parameters.WordSize) {
+          io.bundle.write_strobe(i) := true.B
+        }
+        io.bundle.write_data := io.reg2_data(Parameters.WordSize / 2 * Parameters.ByteBits, 0) << (Parameters
+          .WordSize / 2 * Parameters.ByteBits)
+      }
+    }.elsewhen(io.funct3 === InstructionsTypeS.sw) {
+      for (i <- 0 until Parameters.WordSize) {
+        io.bundle.write_strobe(i) := true.B
+      }
+    }
+  }
+}

lab3/src/main/scala/riscv/core/fivestage_stall/WriteBack.scala

@@ -0,0 +1,40 @@
+// Copyright 2022 Canbin Huang
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.fivestage_stall
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+class WriteBack extends Module {
+  val io = IO(new Bundle() {
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val alu_result = Input(UInt(Parameters.DataWidth))
+    val memory_read_data = Input(UInt(Parameters.DataWidth))
+    val regs_write_source = Input(UInt(2.W))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val regs_write_data = Output(UInt(Parameters.DataWidth))
+  })
+  io.regs_write_data := MuxLookup(
+    io.regs_write_source,
+    io.alu_result,
+    IndexedSeq(
+      RegWriteSource.Memory -> io.memory_read_data,
+      RegWriteSource.CSR -> io.csr_read_data,
+      RegWriteSource.NextInstructionAddress -> (io.instruction_address + 4.U)
+    )
+  )
+}

lab3/src/main/scala/riscv/core/threestage/CLINT.scala

@@ -0,0 +1,88 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.threestage
+
+import chisel3._
+import chisel3.util.MuxLookup
+import riscv.Parameters
+
+object InterruptStatus {
+  val None = 0x0.U(8.W)
+  val Timer0 = 0x1.U(8.W)
+  val Ret = 0xFF.U(8.W)
+}
+
+class CSRDirectAccessBundle extends Bundle {
+  val mstatus = Input(UInt(Parameters.DataWidth))
+  val mepc = Input(UInt(Parameters.DataWidth))
+  val mcause = Input(UInt(Parameters.DataWidth))
+  val mtvec = Input(UInt(Parameters.DataWidth))
+
+  val mstatus_write_data = Output(UInt(Parameters.DataWidth))
+  val mepc_write_data = Output(UInt(Parameters.DataWidth))
+  val mcause_write_data = Output(UInt(Parameters.DataWidth))
+
+  val direct_write_enable = Output(Bool())
+}
+
+// Core Local Interrupt Controller
+class CLINT extends Module {
+  val io = IO(new Bundle {
+    val interrupt_flag = Input(UInt(Parameters.InterruptFlagWidth))
+
+    val instruction_ex = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address_if = Input(UInt(Parameters.AddrWidth))
+    val instruction_address_id = Input(UInt(Parameters.AddrWidth))
+
+    val jump_flag = Input(Bool())
+    val jump_address = Input(UInt(Parameters.AddrWidth))
+
+    val ex_interrupt_handler_address = Output(UInt(Parameters.AddrWidth))
+    val ex_interrupt_assert = Output(Bool())
+
+    val csr_bundle = new CSRDirectAccessBundle
+  })
+  val interrupt_enable = io.csr_bundle.mstatus(3)
+  val jumpping = RegNext(io.jump_flag || io.ex_interrupt_assert)
+  val instruction_address = Mux(
+    io.jump_flag,
+    io.jump_address,
+    Mux(jumpping, io.instruction_address_if, io.instruction_address_id)
+  )
+  val mstatus_disable_interrupt = io.csr_bundle.mstatus(31, 4) ## 0.U(1.W) ## io.csr_bundle.mstatus(2, 0)
+  val mstatus_recover_interrupt = io.csr_bundle.mstatus(31, 4) ## io.csr_bundle.mstatus(7) ## io.csr_bundle.mstatus(2, 0)
+  val exception = io.instruction_ex === InstructionsEnv.ecall || io.instruction_ex === InstructionsEnv.ebreak
+  val interrupt = io.interrupt_flag =/= InterruptStatus.None && interrupt_enable
+  val mret = io.instruction_ex === InstructionsRet.mret
+  val interrupt_assert = exception || interrupt || mret
+
+  io.csr_bundle.mstatus_write_data := Mux(mret, mstatus_recover_interrupt, mstatus_disable_interrupt)
+  io.csr_bundle.mepc_write_data := instruction_address
+  io.csr_bundle.mcause_write_data := Mux(
+    exception,
+    MuxLookup(
+      io.instruction_ex,
+      10.U,
+      IndexedSeq(
+        InstructionsEnv.ecall -> 11.U,
+        InstructionsEnv.ebreak -> 3.U,
+      )
+    ),
+    Mux(io.interrupt_flag(0), 0x80000007L.U, 0x8000000BL.U)
+  )
+  io.csr_bundle.direct_write_enable := interrupt_assert
+  io.ex_interrupt_assert := interrupt_assert
+  io.ex_interrupt_handler_address := Mux(mret, io.csr_bundle.mepc, io.csr_bundle.mtvec)
+}

lab3/src/main/scala/riscv/core/threestage/CPU.scala

@@ -0,0 +1,104 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.threestage
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.{CPUBundle, CSR, RegisterFile}
+
+class CPU extends Module {
+  val io = IO(new CPUBundle)
+
+  val ctrl = Module(new Control)
+  val regs = Module(new RegisterFile)
+  val inst_fetch = Module(new InstructionFetch)
+  val if2id = Module(new IF2ID)
+  val id = Module(new InstructionDecode)
+  val id2ex = Module(new ID2EX)
+  val ex = Module(new Execute)
+  val clint = Module(new CLINT)
+  val csr_regs = Module(new CSR)
+
+  // Lab3(Flush)
+  if2id.io.flush := false.B
+  id2ex.io.flush := false.B
+  // Lab3(Flush) End
+
+  regs.io.write_enable := id2ex.io.output_regs_write_enable
+  regs.io.write_address := id2ex.io.output_regs_write_address
+  regs.io.write_data := ex.io.regs_write_data
+  regs.io.read_address1 := id.io.regs_reg1_read_address
+  regs.io.read_address2 := id.io.regs_reg2_read_address
+  regs.io.debug_read_address := io.debug_read_address
+  io.debug_read_data := regs.io.debug_read_data
+
+  io.instruction_address := inst_fetch.io.instruction_address
+  inst_fetch.io.jump_flag_ex := ex.io.if_jump_flag
+  inst_fetch.io.jump_address_ex := ex.io.if_jump_address
+  inst_fetch.io.rom_instruction := io.instruction
+  inst_fetch.io.instruction_valid := io.instruction_valid
+
+  if2id.io.instruction := inst_fetch.io.id_instruction
+  if2id.io.instruction_address := inst_fetch.io.instruction_address
+  if2id.io.interrupt_flag := io.interrupt_flag
+
+  id.io.instruction := if2id.io.output_instruction
+
+  id2ex.io.instruction := if2id.io.output_instruction
+  id2ex.io.instruction_address := if2id.io.output_instruction_address
+  id2ex.io.reg1_data := regs.io.read_data1
+  id2ex.io.reg2_data := regs.io.read_data2
+  id2ex.io.regs_write_enable := id.io.ex_reg_write_enable
+  id2ex.io.regs_write_address := id.io.ex_reg_write_address
+  id2ex.io.regs_write_source := id.io.ex_reg_write_source
+  id2ex.io.immediate := id.io.ex_immediate
+  id2ex.io.aluop1_source := id.io.ex_aluop1_source
+  id2ex.io.aluop2_source := id.io.ex_aluop2_source
+  id2ex.io.csr_write_enable := id.io.ex_csr_write_enable
+  id2ex.io.csr_address := id.io.ex_csr_address
+  id2ex.io.memory_read_enable := id.io.ex_memory_read_enable
+  id2ex.io.memory_write_enable := id.io.ex_memory_write_enable
+  id2ex.io.csr_read_data := csr_regs.io.id_reg_read_data
+
+  ex.io.instruction := id2ex.io.output_instruction
+  ex.io.instruction_address := id2ex.io.output_instruction_address
+  ex.io.reg1_data := id2ex.io.output_reg1_data
+  ex.io.reg2_data := id2ex.io.output_reg2_data
+  ex.io.csr_read_data := id2ex.io.output_csr_read_data
+  ex.io.immediate_id := id2ex.io.output_immediate
+  ex.io.aluop1_source_id := id2ex.io.output_aluop1_source
+  ex.io.aluop2_source_id := id2ex.io.output_aluop2_source
+  ex.io.memory_read_enable_id := id2ex.io.output_memory_read_enable
+  ex.io.memory_write_enable_id := id2ex.io.output_memory_write_enable
+  ex.io.regs_write_source_id := id2ex.io.output_regs_write_source
+  ex.io.interrupt_assert_clint := clint.io.ex_interrupt_assert
+  ex.io.interrupt_handler_address_clint := clint.io.ex_interrupt_handler_address
+  io.device_select := ex.io.memory_bundle.address(Parameters.AddrBits - 1, Parameters.AddrBits - Parameters.SlaveDeviceCountBits)
+  io.memory_bundle <> ex.io.memory_bundle
+  io.memory_bundle.address := 0.U(Parameters.SlaveDeviceCountBits.W) ## ex.io.memory_bundle.address(Parameters.AddrBits - 1 - Parameters.SlaveDeviceCountBits, 0)
+
+  clint.io.instruction_address_if := inst_fetch.io.instruction_address
+  clint.io.instruction_address_id := if2id.io.output_instruction_address
+  clint.io.instruction_ex := id2ex.io.output_instruction
+  clint.io.jump_flag := ex.io.clint_jump_flag
+  clint.io.jump_address := ex.io.clint_jump_address
+  clint.io.interrupt_flag := if2id.io.output_interrupt_flag
+  clint.io.csr_bundle <> csr_regs.io.clint_access_bundle
+
+  csr_regs.io.reg_read_address_id := id.io.ex_csr_address
+  csr_regs.io.reg_write_enable_ex := id2ex.io.output_csr_write_enable
+  csr_regs.io.reg_write_address_ex := id2ex.io.output_csr_address
+  csr_regs.io.reg_write_data_ex := ex.io.csr_write_data
+}

lab3/src/main/scala/riscv/core/threestage/Control.scala

@@ -0,0 +1,21 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.threestage
+
+import chisel3._
+
+class Control extends Module {
+  // Lab3(Flush)
+}

lab3/src/main/scala/riscv/core/threestage/Execute.scala

@@ -0,0 +1,191 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.threestage
+
+import chisel3._
+import chisel3.util._
+import peripheral.RAMBundle
+import riscv.Parameters
+import riscv.core.{ALU, ALUControl}
+
+
+class Execute extends Module {
+  val io = IO(new Bundle {
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val reg1_data = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+    val immediate_id = Input(UInt(Parameters.DataWidth))
+    val aluop1_source_id = Input(UInt(1.W))
+    val aluop2_source_id = Input(UInt(1.W))
+    val memory_read_enable_id = Input(Bool())
+    val memory_write_enable_id = Input(Bool())
+    val regs_write_source_id = Input(UInt(2.W))
+    val interrupt_assert_clint = Input(Bool())
+    val interrupt_handler_address_clint = Input(UInt(Parameters.AddrWidth))
+
+    val memory_bundle = Flipped(new RAMBundle)
+
+    val csr_write_data = Output(UInt(Parameters.DataWidth))
+    val regs_write_data = Output(UInt(Parameters.DataWidth))
+    val if_jump_flag = Output(Bool())
+    val if_jump_address = Output(UInt(Parameters.AddrWidth))
+    val clint_jump_flag = Output(Bool())
+    val clint_jump_address = Output(UInt(Parameters.AddrWidth))
+  })
+
+  val opcode = io.instruction(6, 0)
+  val funct3 = io.instruction(14, 12)
+  val funct7 = io.instruction(31, 25)
+  val uimm = io.instruction(19, 15)
+
+  // ALU compute
+  val alu = Module(new ALU)
+  val alu_ctrl = Module(new ALUControl)
+
+  alu_ctrl.io.opcode := opcode
+  alu_ctrl.io.funct3 := funct3
+  alu_ctrl.io.funct7 := funct7
+  alu.io.func := alu_ctrl.io.alu_funct
+  alu.io.op1 := Mux(
+    io.aluop1_source_id === ALUOp1Source.InstructionAddress,
+    io.instruction_address,
+    io.reg1_data
+  )
+  alu.io.op2 := Mux(
+    io.aluop2_source_id === ALUOp2Source.Immediate,
+    io.immediate_id,
+    io.reg2_data
+  )
+  io.csr_write_data := MuxLookup(
+    funct3,
+    0.U,
+    IndexedSeq(
+      InstructionsTypeCSR.csrrw -> io.reg1_data,
+      InstructionsTypeCSR.csrrc -> (io.csr_read_data & (~io.reg1_data).asUInt),
+      InstructionsTypeCSR.csrrs -> (io.csr_read_data | io.reg1_data),
+      InstructionsTypeCSR.csrrwi -> (0.U(27.W) ## uimm),
+      InstructionsTypeCSR.csrrci -> (io.csr_read_data & (~(0.U(27.W) ## uimm)).asUInt),
+      InstructionsTypeCSR.csrrsi -> (io.csr_read_data | 0.U(27.W) ## uimm),
+    )
+  )
+
+  // memory access
+  val mem_address_index = alu.io.result(log2Up(Parameters.WordSize) - 1, 0).asUInt
+  val mem_read_data = Wire(UInt(Parameters.DataWidth))
+  io.memory_bundle.write_enable := io.memory_write_enable_id
+  io.memory_bundle.write_data := 0.U
+  io.memory_bundle.address := alu.io.result
+  io.memory_bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(false.B))
+  mem_read_data := 0.U
+
+  when(io.memory_read_enable_id) {
+    val data = io.memory_bundle.read_data
+    mem_read_data := MuxLookup(
+      funct3,
+      0.U,
+      IndexedSeq(
+        InstructionsTypeL.lb -> MuxLookup(
+          mem_address_index,
+          Cat(Fill(24, data(31)), data(31, 24)),
+          IndexedSeq(
+            0.U -> Cat(Fill(24, data(7)), data(7, 0)),
+            1.U -> Cat(Fill(24, data(15)), data(15, 8)),
+            2.U -> Cat(Fill(24, data(23)), data(23, 16))
+          )
+        ),
+        InstructionsTypeL.lbu -> MuxLookup(
+          mem_address_index,
+          Cat(Fill(24, 0.U), data(31, 24)),
+          IndexedSeq(
+            0.U -> Cat(Fill(24, 0.U), data(7, 0)),
+            1.U -> Cat(Fill(24, 0.U), data(15, 8)),
+            2.U -> Cat(Fill(24, 0.U), data(23, 16))
+          )
+        ),
+        InstructionsTypeL.lh -> Mux(
+          mem_address_index === 0.U,
+          Cat(Fill(16, data(15)), data(15, 0)),
+          Cat(Fill(16, data(31)), data(31, 16))
+        ),
+        InstructionsTypeL.lhu -> Mux(
+          mem_address_index === 0.U,
+          Cat(Fill(16, 0.U), data(15, 0)),
+          Cat(Fill(16, 0.U), data(31, 16))
+        ),
+        InstructionsTypeL.lw -> data
+      )
+    )
+  }.elsewhen(io.memory_write_enable_id) {
+    io.memory_bundle.write_data := io.reg2_data
+    io.memory_bundle.write_strobe := VecInit(Seq.fill(Parameters.WordSize)(false.B))
+    when(funct3 === InstructionsTypeS.sb) {
+      io.memory_bundle.write_strobe(mem_address_index) := true.B
+      io.memory_bundle.write_data := io.reg2_data(Parameters.ByteBits, 0) << (mem_address_index << log2Up(Parameters.ByteBits).U)
+    }.elsewhen(funct3 === InstructionsTypeS.sh) {
+      when(mem_address_index === 0.U) {
+        for (i <- 0 until Parameters.WordSize / 2) {
+          io.memory_bundle.write_strobe(i) := true.B
+        }
+        io.memory_bundle.write_data := io.reg2_data(Parameters.WordSize / 2 * Parameters.ByteBits, 0)
+      }.otherwise {
+        for (i <- Parameters.WordSize / 2 until Parameters.WordSize) {
+          io.memory_bundle.write_strobe(i) := true.B
+        }
+        io.memory_bundle.write_data := io.reg2_data(Parameters.WordSize / 2 * Parameters.ByteBits, 0) << (Parameters
+          .WordSize / 2 * Parameters.ByteBits)
+      }
+    }.elsewhen(funct3 === InstructionsTypeS.sw) {
+      for (i <- 0 until Parameters.WordSize) {
+        io.memory_bundle.write_strobe(i) := true.B
+      }
+    }
+  }
+
+  // write back
+  io.regs_write_data := MuxLookup(
+    io.regs_write_source_id,
+    alu.io.result,
+    IndexedSeq(
+      RegWriteSource.Memory -> mem_read_data,
+      RegWriteSource.CSR -> io.csr_read_data,
+      RegWriteSource.NextInstructionAddress -> (io.instruction_address + 4.U)
+    )
+  )
+
+  // jump and interrupt
+  val instruction_jump_flag = (opcode === Instructions.jal) ||
+    (opcode === Instructions.jalr) ||
+    (opcode === InstructionTypes.B) && MuxLookup(
+      funct3,
+      false.B,
+      IndexedSeq(
+        InstructionsTypeB.beq -> (io.reg1_data === io.reg2_data),
+        InstructionsTypeB.bne -> (io.reg1_data =/= io.reg2_data),
+        InstructionsTypeB.blt -> (io.reg1_data.asSInt < io.reg2_data.asSInt),
+        InstructionsTypeB.bge -> (io.reg1_data.asSInt >= io.reg2_data.asSInt),
+        InstructionsTypeB.bltu -> (io.reg1_data.asUInt < io.reg2_data.asUInt),
+        InstructionsTypeB.bgeu -> (io.reg1_data.asUInt >= io.reg2_data.asUInt)
+      )
+    )
+  io.clint_jump_flag := instruction_jump_flag
+  io.clint_jump_address := alu.io.result
+  io.if_jump_flag := io.interrupt_assert_clint || instruction_jump_flag
+  io.if_jump_address := Mux(io.interrupt_assert_clint,
+    io.interrupt_handler_address_clint,
+    alu.io.result
+  )
+}

lab3/src/main/scala/riscv/core/threestage/ID2EX.scala

@@ -0,0 +1,148 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.threestage
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class ID2EX extends Module {
+  val io = IO(new Bundle {
+    val flush = Input(Bool())
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val regs_write_enable = Input(Bool())
+    val regs_write_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_write_source = Input(UInt(2.W))
+    val reg1_data = Input(UInt(Parameters.DataWidth))
+    val reg2_data = Input(UInt(Parameters.DataWidth))
+    val immediate = Input(UInt(Parameters.DataWidth))
+    val aluop1_source = Input(UInt(1.W))
+    val aluop2_source = Input(UInt(1.W))
+    val csr_write_enable = Input(Bool())
+    val csr_address = Input(UInt(Parameters.CSRRegisterAddrWidth))
+    val memory_read_enable = Input(Bool())
+    val memory_write_enable = Input(Bool())
+    val csr_read_data = Input(UInt(Parameters.DataWidth))
+
+    val output_instruction = Output(UInt(Parameters.DataWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_regs_write_enable = Output(Bool())
+    val output_regs_write_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val output_regs_write_source = Output(UInt(2.W))
+    val output_reg1_data = Output(UInt(Parameters.DataWidth))
+    val output_reg2_data = Output(UInt(Parameters.DataWidth))
+    val output_immediate = Output(UInt(Parameters.DataWidth))
+    val output_aluop1_source = Output(UInt(1.W))
+    val output_aluop2_source = Output(UInt(1.W))
+    val output_csr_write_enable = Output(Bool())
+    val output_csr_address = Output(UInt(Parameters.CSRRegisterAddrWidth))
+    val output_memory_read_enable = Output(Bool())
+    val output_memory_write_enable = Output(Bool())
+    val output_csr_read_data = Output(UInt(Parameters.DataWidth))
+  })
+
+  val stall = false.B
+
+  val instruction = Module(new PipelineRegister(defaultValue = InstructionsNop.nop))
+  instruction.io.in := io.instruction
+  instruction.io.stall := stall
+  instruction.io.flush := io.flush
+  io.output_instruction := instruction.io.out
+
+  val instruction_address = Module(new PipelineRegister(defaultValue = ProgramCounter.EntryAddress))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := io.flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val regs_write_enable = Module(new PipelineRegister(1))
+  regs_write_enable.io.in := io.regs_write_enable
+  regs_write_enable.io.stall := stall
+  regs_write_enable.io.flush := io.flush
+  io.output_regs_write_enable := regs_write_enable.io.out
+
+  val regs_write_address = Module(new PipelineRegister(Parameters.PhysicalRegisterAddrBits))
+  regs_write_address.io.in := io.regs_write_address
+  regs_write_address.io.stall := stall
+  regs_write_address.io.flush := io.flush
+  io.output_regs_write_address := regs_write_address.io.out
+
+  val regs_write_source = Module(new PipelineRegister(2))
+  regs_write_source.io.in := io.regs_write_source
+  regs_write_source.io.stall := stall
+  regs_write_source.io.flush := io.flush
+  io.output_regs_write_source := regs_write_source.io.out
+
+  val reg1_data = Module(new PipelineRegister())
+  reg1_data.io.in := io.reg1_data
+  reg1_data.io.stall := stall
+  reg1_data.io.flush := io.flush
+  io.output_reg1_data := reg1_data.io.out
+
+  val reg2_data = Module(new PipelineRegister())
+  reg2_data.io.in := io.reg2_data
+  reg2_data.io.stall := stall
+  reg2_data.io.flush := io.flush
+  io.output_reg2_data := reg2_data.io.out
+
+  val immediate = Module(new PipelineRegister())
+  immediate.io.in := io.immediate
+  immediate.io.stall := stall
+  immediate.io.flush := io.flush
+  io.output_immediate := immediate.io.out
+
+  val aluop1_source = Module(new PipelineRegister(1))
+  aluop1_source.io.in := io.aluop1_source
+  aluop1_source.io.stall := stall
+  aluop1_source.io.flush := io.flush
+  io.output_aluop1_source := aluop1_source.io.out
+
+  val aluop2_source = Module(new PipelineRegister(1))
+  aluop2_source.io.in := io.aluop2_source
+  aluop2_source.io.stall := stall
+  aluop2_source.io.flush := io.flush
+  io.output_aluop2_source := aluop2_source.io.out
+
+  val csr_write_enable = Module(new PipelineRegister(1))
+  csr_write_enable.io.in := io.csr_write_enable
+  csr_write_enable.io.stall := stall
+  csr_write_enable.io.flush := io.flush
+  io.output_csr_write_enable := csr_write_enable.io.out
+
+  val csr_address = Module(new PipelineRegister(Parameters.CSRRegisterAddrBits))
+  csr_address.io.in := io.csr_address
+  csr_address.io.stall := stall
+  csr_address.io.flush := io.flush
+  io.output_csr_address := csr_address.io.out
+
+  val memory_read_enable = Module(new PipelineRegister(1))
+  memory_read_enable.io.in := io.memory_read_enable
+  memory_read_enable.io.stall := stall
+  memory_read_enable.io.flush := io.flush
+  io.output_memory_read_enable := memory_read_enable.io.out
+
+  val memory_write_enable = Module(new PipelineRegister(1))
+  memory_write_enable.io.in := io.memory_write_enable
+  memory_write_enable.io.stall := stall
+  memory_write_enable.io.flush := io.flush
+  io.output_memory_write_enable := memory_write_enable.io.out
+
+  val csr_read_data = Module(new PipelineRegister())
+  csr_read_data.io.in := io.csr_read_data
+  csr_read_data.io.stall := stall
+  csr_read_data.io.flush := io.flush
+  io.output_csr_read_data := csr_read_data.io.out
+}

lab3/src/main/scala/riscv/core/threestage/IF2ID.scala

@@ -0,0 +1,52 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.threestage
+
+import chisel3._
+import riscv.Parameters
+import riscv.core.PipelineRegister
+
+class IF2ID extends Module {
+  val io = IO(new Bundle {
+    val flush = Input(Bool())
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+    val instruction_address = Input(UInt(Parameters.AddrWidth))
+    val interrupt_flag = Input(UInt(Parameters.InterruptFlagWidth))
+
+    val output_instruction = Output(UInt(Parameters.DataWidth))
+    val output_instruction_address = Output(UInt(Parameters.AddrWidth))
+    val output_interrupt_flag = Output(UInt(Parameters.InterruptFlagWidth))
+  })
+
+  val stall = false.B
+
+  val instruction = Module(new PipelineRegister(defaultValue = InstructionsNop.nop))
+  instruction.io.in := io.instruction
+  instruction.io.stall := stall
+  instruction.io.flush := io.flush
+  io.output_instruction := instruction.io.out
+
+  val instruction_address = Module(new PipelineRegister(defaultValue = ProgramCounter.EntryAddress))
+  instruction_address.io.in := io.instruction_address
+  instruction_address.io.stall := stall
+  instruction_address.io.flush := io.flush
+  io.output_instruction_address := instruction_address.io.out
+
+  val interrupt_flag = Module(new PipelineRegister(Parameters.InterruptFlagBits))
+  interrupt_flag.io.in := io.interrupt_flag
+  interrupt_flag.io.stall := stall
+  interrupt_flag.io.flush := io.flush
+  io.output_interrupt_flag := interrupt_flag.io.out
+}

lab3/src/main/scala/riscv/core/threestage/InstructionDecode.scala

@@ -0,0 +1,207 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.threestage
+
+import chisel3._
+import chisel3.util._
+import riscv.Parameters
+
+object InstructionTypes {
+  val L = "b0000011".U
+  val I = "b0010011".U
+  val S = "b0100011".U
+  val RM = "b0110011".U
+  val B = "b1100011".U
+}
+
+object Instructions {
+  val lui = "b0110111".U
+  val nop = "b0000001".U
+  val jal = "b1101111".U
+  val jalr = "b1100111".U
+  val auipc = "b0010111".U
+  val csr = "b1110011".U
+  val fence = "b0001111".U
+}
+
+object InstructionsTypeL {
+  val lb = "b000".U
+  val lh = "b001".U
+  val lw = "b010".U
+  val lbu = "b100".U
+  val lhu = "b101".U
+}
+
+object InstructionsTypeI {
+  val addi = 0.U
+  val slli = 1.U
+  val slti = 2.U
+  val sltiu = 3.U
+  val xori = 4.U
+  val sri = 5.U
+  val ori = 6.U
+  val andi = 7.U
+}
+
+object InstructionsTypeS {
+  val sb = "b000".U
+  val sh = "b001".U
+  val sw = "b010".U
+}
+
+object InstructionsTypeR {
+  val add_sub = 0.U
+  val sll = 1.U
+  val slt = 2.U
+  val sltu = 3.U
+  val xor = 4.U
+  val sr = 5.U
+  val or = 6.U
+  val and = 7.U
+}
+
+object InstructionsTypeM {
+  val mul = 0.U
+  val mulh = 1.U
+  val mulhsu = 2.U
+  val mulhum = 3.U
+  val div = 4.U
+  val divu = 5.U
+  val rem = 6.U
+  val remu = 7.U
+}
+
+object InstructionsTypeB {
+  val beq = "b000".U
+  val bne = "b001".U
+  val blt = "b100".U
+  val bge = "b101".U
+  val bltu = "b110".U
+  val bgeu = "b111".U
+}
+
+object InstructionsTypeCSR {
+  val csrrw = "b001".U
+  val csrrs = "b010".U
+  val csrrc = "b011".U
+  val csrrwi = "b101".U
+  val csrrsi = "b110".U
+  val csrrci = "b111".U
+}
+
+object InstructionsNop {
+  val nop = 0x00000013L.U(Parameters.DataWidth)
+}
+
+object InstructionsRet {
+  val mret = 0x30200073L.U(Parameters.DataWidth)
+  val ret = 0x00008067L.U(Parameters.DataWidth)
+}
+
+object InstructionsEnv {
+  val ecall = 0x00000073L.U(Parameters.DataWidth)
+  val ebreak = 0x00100073L.U(Parameters.DataWidth)
+}
+
+object ALUOp1Source {
+  val Register = 0.U(1.W)
+  val InstructionAddress = 1.U(1.W)
+}
+
+object ALUOp2Source {
+  val Register = 0.U(1.W)
+  val Immediate = 1.U(1.W)
+}
+
+object RegWriteSource {
+  val ALUResult = 0.U(2.W)
+  val Memory = 1.U(2.W)
+  val CSR = 2.U(2.W)
+  val NextInstructionAddress = 3.U(2.W)
+}
+
+class InstructionDecode extends Module {
+  val io = IO(new Bundle {
+    val instruction = Input(UInt(Parameters.InstructionWidth))
+
+    val regs_reg1_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val regs_reg2_read_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val ex_immediate = Output(UInt(Parameters.DataWidth))
+    val ex_aluop1_source = Output(Bool())
+    val ex_aluop2_source = Output(Bool())
+    val ex_memory_read_enable = Output(Bool())
+    val ex_memory_write_enable = Output(Bool())
+    val ex_reg_write_source = Output(UInt(2.W))
+    val ex_reg_write_enable = Output(Bool())
+    val ex_reg_write_address = Output(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val ex_csr_address = Output(UInt(Parameters.CSRRegisterAddrWidth))
+    val ex_csr_write_enable = Output(Bool())
+  })
+  val opcode = io.instruction(6, 0)
+  val funct3 = io.instruction(14, 12)
+  val funct7 = io.instruction(31, 25)
+  val rd = io.instruction(11, 7)
+  val rs1 = io.instruction(19, 15)
+  val rs2 = io.instruction(24, 20)
+
+  io.regs_reg1_read_address := Mux(opcode === Instructions.lui, 0.U(Parameters.PhysicalRegisterAddrWidth), rs1)
+  io.regs_reg2_read_address := rs2
+  io.ex_immediate := MuxLookup(
+    opcode,
+    Cat(Fill(20, io.instruction(31)), io.instruction(31, 20)),
+    IndexedSeq(
+      InstructionTypes.I -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      InstructionTypes.L -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      Instructions.jalr -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 20)),
+      InstructionTypes.S -> Cat(Fill(21, io.instruction(31)), io.instruction(30, 25), io.instruction(11, 7)),
+      InstructionTypes.B -> Cat(Fill(20, io.instruction(31)), io.instruction(7), io.instruction(30, 25), io.instruction(11, 8), 0.U(1.W)),
+      Instructions.lui -> Cat(io.instruction(31, 12), 0.U(12.W)),
+      Instructions.auipc -> Cat(io.instruction(31, 12), 0.U(12.W)),
+      Instructions.jal -> Cat(Fill(12, io.instruction(31)), io.instruction(19, 12), io.instruction(20), io.instruction(30, 21), 0.U(1.W))
+    )
+  )
+  io.ex_aluop1_source := Mux(
+    opcode === Instructions.auipc || opcode === InstructionTypes.B || opcode === Instructions.jal,
+    ALUOp1Source.InstructionAddress,
+    ALUOp1Source.Register
+  )
+  io.ex_aluop2_source := Mux(
+    opcode === InstructionTypes.RM,
+    ALUOp2Source.Register,
+    ALUOp2Source.Immediate
+  )
+  io.ex_memory_read_enable := opcode === InstructionTypes.L
+  io.ex_memory_write_enable := opcode === InstructionTypes.S
+  io.ex_reg_write_source := MuxLookup(
+    opcode,
+    RegWriteSource.ALUResult,
+    IndexedSeq(
+      InstructionTypes.L -> RegWriteSource.Memory,
+      Instructions.csr -> RegWriteSource.CSR,
+      Instructions.jal -> RegWriteSource.NextInstructionAddress,
+      Instructions.jalr -> RegWriteSource.NextInstructionAddress
+    )
+  )
+  io.ex_reg_write_enable := (opcode === InstructionTypes.RM) || (opcode === InstructionTypes.I) ||
+    (opcode === InstructionTypes.L) || (opcode === Instructions.auipc) || (opcode === Instructions.lui) ||
+    (opcode === Instructions.jal) || (opcode === Instructions.jalr) || (opcode === Instructions.csr)
+  io.ex_reg_write_address := rd
+  io.ex_csr_address := io.instruction(31, 20)
+  io.ex_csr_write_enable := (opcode === Instructions.csr) && (
+    funct3 === InstructionsTypeCSR.csrrw || funct3 === InstructionsTypeCSR.csrrwi ||
+      funct3 === InstructionsTypeCSR.csrrs || funct3 === InstructionsTypeCSR.csrrsi ||
+      funct3 === InstructionsTypeCSR.csrrc || funct3 === InstructionsTypeCSR.csrrci
+    )
+}

lab3/src/main/scala/riscv/core/threestage/InstructionFetch.scala

@@ -0,0 +1,47 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv.core.threestage
+
+import chisel3._
+import chisel3.util.MuxCase
+import riscv.Parameters
+
+object ProgramCounter {
+  val EntryAddress = Parameters.EntryAddress
+}
+
+class InstructionFetch extends Module {
+  val io = IO(new Bundle {
+    val jump_flag_ex = Input(Bool())
+    val jump_address_ex = Input(UInt(Parameters.AddrWidth))
+    val rom_instruction = Input(UInt(Parameters.DataWidth))
+    val instruction_valid = Input(Bool())
+
+    val instruction_address = Output(UInt(Parameters.AddrWidth))
+    val id_instruction = Output(UInt(Parameters.InstructionWidth))
+  })
+  val pc = RegInit(ProgramCounter.EntryAddress)
+
+  pc := MuxCase(
+    pc,
+    IndexedSeq(
+      io.jump_flag_ex -> io.jump_address_ex,
+      io.instruction_valid -> (pc + 4.U)
+    )
+  )
+
+  io.instruction_address := pc
+  io.id_instruction := Mux(io.instruction_valid, io.rom_instruction, InstructionsNop.nop)
+}

lab3/src/test/scala/riscv/FiveStageCPUFinalTest.scala

@@ -0,0 +1,73 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv
+
+import chisel3._
+import chiseltest._
+import org.scalatest.flatspec.AnyFlatSpec
+
+
+class FiveStageCPUFinalTest extends AnyFlatSpec with ChiselScalatestTester {
+  behavior of "Five-stage Pipelined CPU with Reduced Branch Delay"
+  it should "calculate recursively fibonacci(10)" in {
+    test(new TestTopModule("fibonacci.asmbin", ImplementationType.FiveStageFinal)).withAnnotations(TestAnnotations.annos) { c =>
+      for (i <- 1 to 50) {
+        c.clock.step(1000)
+        c.io.mem_debug_read_address.poke((i * 4).U) // Avoid timeout
+      }
+
+      c.io.mem_debug_read_address.poke(4.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(55.U)
+    }
+  }
+  it should "quicksort 10 numbers" in {
+    test(new TestTopModule("quicksort.asmbin", ImplementationType.FiveStageFinal)).withAnnotations(TestAnnotations.annos) { c =>
+      for (i <- 1 to 50) {
+        c.clock.step(1000)
+        c.io.mem_debug_read_address.poke((i * 4).U) // Avoid timeout
+      }
+      for (i <- 1 to 10) {
+        c.io.mem_debug_read_address.poke((4 * i).U)
+        c.clock.step()
+        c.io.mem_debug_read_data.expect((i - 1).U)
+      }
+    }
+  }
+  it should "store and load single byte" in {
+    test(new TestTopModule("sb.asmbin", ImplementationType.FiveStageFinal)).withAnnotations(TestAnnotations.annos) { c =>
+      c.clock.step(1000)
+      c.io.regs_debug_read_address.poke(5.U)
+      c.io.regs_debug_read_data.expect(0xDEADBEEFL.U)
+      c.io.regs_debug_read_address.poke(6.U)
+      c.io.regs_debug_read_data.expect(0xEF.U)
+      c.io.regs_debug_read_address.poke(1.U)
+      c.io.regs_debug_read_data.expect(0x15EF.U)
+    }
+  }
+  it should "solve data and control hazards" in {
+    test(new TestTopModule("hazard.asmbin", ImplementationType.FiveStageFinal)).withAnnotations(TestAnnotations.annos) { c =>
+      c.clock.step(1000)
+      c.io.regs_debug_read_address.poke(1.U)
+      c.io.regs_debug_read_data.expect(26.U)
+      c.io.mem_debug_read_address.poke(4.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(1.U)
+      c.io.mem_debug_read_address.poke(8.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(3.U)
+    }
+  }
+}

lab3/src/test/scala/riscv/FiveStageCPUForwardTest.scala

@@ -0,0 +1,73 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv
+
+import chisel3._
+import chiseltest._
+import org.scalatest.flatspec.AnyFlatSpec
+
+
+class FiveStageCPUForwardTest extends AnyFlatSpec with ChiselScalatestTester {
+  behavior of "Five-stage Pipelined CPU with Forwarding"
+  it should "calculate recursively fibonacci(10)" in {
+    test(new TestTopModule("fibonacci.asmbin", ImplementationType.FiveStageForward)).withAnnotations(TestAnnotations.annos) { c =>
+      for (i <- 1 to 50) {
+        c.clock.step(1000)
+        c.io.mem_debug_read_address.poke((i * 4).U) // Avoid timeout
+      }
+
+      c.io.mem_debug_read_address.poke(4.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(55.U)
+    }
+  }
+  it should "quicksort 10 numbers" in {
+    test(new TestTopModule("quicksort.asmbin", ImplementationType.FiveStageForward)).withAnnotations(TestAnnotations.annos) { c =>
+      for (i <- 1 to 50) {
+        c.clock.step(1000)
+        c.io.mem_debug_read_address.poke((i * 4).U) // Avoid timeout
+      }
+      for (i <- 1 to 10) {
+        c.io.mem_debug_read_address.poke((4 * i).U)
+        c.clock.step()
+        c.io.mem_debug_read_data.expect((i - 1).U)
+      }
+    }
+  }
+  it should "store and load single byte" in {
+    test(new TestTopModule("sb.asmbin", ImplementationType.FiveStageForward)).withAnnotations(TestAnnotations.annos) { c =>
+      c.clock.step(1000)
+      c.io.regs_debug_read_address.poke(5.U)
+      c.io.regs_debug_read_data.expect(0xDEADBEEFL.U)
+      c.io.regs_debug_read_address.poke(6.U)
+      c.io.regs_debug_read_data.expect(0xEF.U)
+      c.io.regs_debug_read_address.poke(1.U)
+      c.io.regs_debug_read_data.expect(0x15EF.U)
+    }
+  }
+  it should "solve data and control hazards" in {
+    test(new TestTopModule("hazard.asmbin", ImplementationType.FiveStageForward)).withAnnotations(TestAnnotations.annos) { c =>
+      c.clock.step(1000)
+      c.io.regs_debug_read_address.poke(1.U)
+      c.io.regs_debug_read_data.expect(27.U)
+      c.io.mem_debug_read_address.poke(4.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(1.U)
+      c.io.mem_debug_read_address.poke(8.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(3.U)
+    }
+  }
+}

lab3/src/test/scala/riscv/FiveStageCPUStallTest.scala

@@ -0,0 +1,73 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv
+
+import chisel3._
+import chiseltest._
+import org.scalatest.flatspec.AnyFlatSpec
+
+
+class FiveStageCPUStallTest extends AnyFlatSpec with ChiselScalatestTester {
+  behavior of "Five-stage Pipelined CPU with Stalling"
+  it should "calculate recursively fibonacci(10)" in {
+    test(new TestTopModule("fibonacci.asmbin", ImplementationType.FiveStageStall)).withAnnotations(TestAnnotations.annos) { c =>
+      for (i <- 1 to 50) {
+        c.clock.step(1000)
+        c.io.mem_debug_read_address.poke((i * 4).U) // Avoid timeout
+      }
+
+      c.io.mem_debug_read_address.poke(4.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(55.U)
+    }
+  }
+  it should "quicksort 10 numbers" in {
+    test(new TestTopModule("quicksort.asmbin", ImplementationType.FiveStageStall)).withAnnotations(TestAnnotations.annos) { c =>
+      for (i <- 1 to 50) {
+        c.clock.step(1000)
+        c.io.mem_debug_read_address.poke((i * 4).U) // Avoid timeout
+      }
+      for (i <- 1 to 10) {
+        c.io.mem_debug_read_address.poke((4 * i).U)
+        c.clock.step()
+        c.io.mem_debug_read_data.expect((i - 1).U)
+      }
+    }
+  }
+  it should "store and load single byte" in {
+    test(new TestTopModule("sb.asmbin", ImplementationType.FiveStageStall)).withAnnotations(TestAnnotations.annos) { c =>
+      c.clock.step(1000)
+      c.io.regs_debug_read_address.poke(5.U)
+      c.io.regs_debug_read_data.expect(0xDEADBEEFL.U)
+      c.io.regs_debug_read_address.poke(6.U)
+      c.io.regs_debug_read_data.expect(0xEF.U)
+      c.io.regs_debug_read_address.poke(1.U)
+      c.io.regs_debug_read_data.expect(0x15EF.U)
+    }
+  }
+  it should "solve data and control hazards" in {
+    test(new TestTopModule("hazard.asmbin", ImplementationType.FiveStageStall)).withAnnotations(TestAnnotations.annos) { c =>
+      c.clock.step(1000)
+      c.io.regs_debug_read_address.poke(1.U)
+      c.io.regs_debug_read_data.expect(46.U)
+      c.io.mem_debug_read_address.poke(4.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(1.U)
+      c.io.mem_debug_read_address.poke(8.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(3.U)
+    }
+  }
+}

lab3/src/test/scala/riscv/PipelineRegisterTest.scala

@@ -0,0 +1,58 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv
+
+import chisel3._
+import chiseltest._
+import org.scalatest.flatspec.AnyFlatSpec
+import riscv.core.PipelineRegister
+
+import scala.math.pow
+import scala.util.Random
+
+
+class PipelineRegisterTest extends AnyFlatSpec with ChiselScalatestTester {
+  behavior of "Pipeline Register"
+  it should "be able to stall and flush" in {
+    val rand = new Random
+    val default_value = rand.nextInt(pow(2, Parameters.DataBits).toInt).asUInt(Parameters.DataWidth)
+    test(new PipelineRegister(Parameters.DataBits, default_value)).withAnnotations(TestAnnotations.annos) { c =>
+      var pre = default_value
+      for (_ <- 1 to 1000) {
+        val cur = rand.nextInt(pow(2, Parameters.DataBits).toInt).asUInt(Parameters.DataWidth)
+        c.io.in.poke(cur)
+        rand.nextInt(3) match {
+          case 0 =>
+            c.io.stall.poke(false.B)
+            c.io.flush.poke(false.B)
+            c.clock.step()
+            c.io.out.expect(cur)
+            pre = cur
+          case 1 =>
+            c.io.stall.poke(true.B)
+            c.io.flush.poke(false.B)
+            c.clock.step()
+            c.io.out.expect(pre)
+          case 2 =>
+            c.io.stall.poke(false.B)
+            c.io.flush.poke(true.B)
+            c.clock.step()
+            c.io.out.expect(default_value)
+            pre = default_value
+        }
+      }
+    }
+  }
+}

lab3/src/test/scala/riscv/TestAnnotations.scala

@@ -0,0 +1,52 @@
+// Copyright 2022 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv
+
+import chiseltest.{VerilatorBackendAnnotation, WriteVcdAnnotation}
+import firrtl.AnnotationSeq
+
+import java.nio.file.{Files, Paths}
+
+object VerilatorEnabler {
+  val annos: AnnotationSeq = if (sys.env.contains("Path")) {
+    if (sys.env.getOrElse("Path", "").split(";").exists(path => {
+      Files.exists(Paths.get(path, "verilator"))
+    })) {
+      Seq(VerilatorBackendAnnotation)
+    } else {
+      Seq()
+    }
+  } else {
+    if (sys.env.getOrElse("PATH", "").split(":").exists(path => {
+      Files.exists(Paths.get(path, "verilator"))
+    })) {
+      Seq(VerilatorBackendAnnotation)
+    } else {
+      Seq()
+    }
+  }
+}
+
+object WriteVcdEnabler {
+  val annos: AnnotationSeq = if (sys.env.contains("WRITE_VCD")) {
+    Seq(WriteVcdAnnotation)
+  } else {
+    Seq()
+  }
+}
+
+object TestAnnotations {
+  val annos = VerilatorEnabler.annos ++ WriteVcdEnabler.annos
+}

lab3/src/test/scala/riscv/TestTopModule.scala

@@ -0,0 +1,66 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv
+
+import chisel3._
+import peripheral.{InstructionROM, Memory, ROMLoader}
+import riscv.core.CPU
+
+class TestTopModule(exeFilename: String, implementation: Int) extends Module {
+  val io = IO(new Bundle {
+    val regs_debug_read_address = Input(UInt(Parameters.PhysicalRegisterAddrWidth))
+    val mem_debug_read_address = Input(UInt(Parameters.AddrWidth))
+    val regs_debug_read_data = Output(UInt(Parameters.DataWidth))
+    val mem_debug_read_data = Output(UInt(Parameters.DataWidth))
+  })
+
+  val mem = Module(new Memory(8192))
+  val instruction_rom = Module(new InstructionROM(exeFilename))
+  val rom_loader = Module(new ROMLoader(instruction_rom.capacity))
+
+  rom_loader.io.rom_data := instruction_rom.io.data
+  rom_loader.io.load_address := Parameters.EntryAddress
+  instruction_rom.io.address := rom_loader.io.rom_address
+
+  val CPU_clkdiv = RegInit(UInt(2.W), 0.U)
+  val CPU_tick = Wire(Bool())
+  val CPU_next = Wire(UInt(2.W))
+  CPU_next := Mux(CPU_clkdiv === 3.U, 0.U, CPU_clkdiv + 1.U)
+  CPU_tick := CPU_clkdiv === 0.U
+  CPU_clkdiv := CPU_next
+
+  withClock(CPU_tick.asClock) {
+    val cpu = Module(new CPU(implementation))
+    cpu.io.debug_read_address := 0.U
+    cpu.io.instruction_valid := rom_loader.io.load_finished
+    mem.io.instruction_address := cpu.io.instruction_address
+    cpu.io.instruction := mem.io.instruction
+    cpu.io.interrupt_flag := 0.U
+
+    when(!rom_loader.io.load_finished) {
+      rom_loader.io.bundle <> mem.io.bundle
+      cpu.io.memory_bundle.read_data := 0.U
+    }.otherwise {
+      rom_loader.io.bundle.read_data := 0.U
+      cpu.io.memory_bundle <> mem.io.bundle
+    }
+
+    cpu.io.debug_read_address := io.regs_debug_read_address
+    io.regs_debug_read_data := cpu.io.debug_read_data
+  }
+
+  mem.io.debug_read_address := io.mem_debug_read_address
+  io.mem_debug_read_data := mem.io.debug_read_data
+}

lab3/src/test/scala/riscv/ThreeStageCPUTest.scala

@@ -0,0 +1,73 @@
+// Copyright 2021 Howard Lau
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package riscv
+
+import chisel3._
+import chiseltest._
+import org.scalatest.flatspec.AnyFlatSpec
+
+
+class ThreeStageCPUTest extends AnyFlatSpec with ChiselScalatestTester {
+  behavior of "Three-stage Pipelined CPU"
+  it should "calculate recursively fibonacci(10)" in {
+    test(new TestTopModule("fibonacci.asmbin", ImplementationType.ThreeStage)).withAnnotations(TestAnnotations.annos) { c =>
+      for (i <- 1 to 50) {
+        c.clock.step(1000)
+        c.io.mem_debug_read_address.poke((i * 4).U) // Avoid timeout
+      }
+
+      c.io.mem_debug_read_address.poke(4.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(55.U)
+    }
+  }
+  it should "quicksort 10 numbers" in {
+    test(new TestTopModule("quicksort.asmbin", ImplementationType.ThreeStage)).withAnnotations(TestAnnotations.annos) { c =>
+      for (i <- 1 to 50) {
+        c.clock.step(1000)
+        c.io.mem_debug_read_address.poke((i * 4).U) // Avoid timeout
+      }
+      for (i <- 1 to 10) {
+        c.io.mem_debug_read_address.poke((4 * i).U)
+        c.clock.step()
+        c.io.mem_debug_read_data.expect((i - 1).U)
+      }
+    }
+  }
+  it should "store and load single byte" in {
+    test(new TestTopModule("sb.asmbin", ImplementationType.ThreeStage)).withAnnotations(TestAnnotations.annos) { c =>
+      c.clock.step(1000)
+      c.io.regs_debug_read_address.poke(5.U)
+      c.io.regs_debug_read_data.expect(0xDEADBEEFL.U)
+      c.io.regs_debug_read_address.poke(6.U)
+      c.io.regs_debug_read_data.expect(0xEF.U)
+      c.io.regs_debug_read_address.poke(1.U)
+      c.io.regs_debug_read_data.expect(0x15EF.U)
+    }
+  }
+  it should "solve control hazards" in {
+    test(new TestTopModule("hazard.asmbin", ImplementationType.ThreeStage)).withAnnotations(TestAnnotations.annos) { c =>
+      c.clock.step(1000)
+      c.io.regs_debug_read_address.poke(1.U)
+      c.io.regs_debug_read_data.expect(26.U)
+      c.io.mem_debug_read_address.poke(4.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(1.U)
+      c.io.mem_debug_read_address.poke(8.U)
+      c.clock.step()
+      c.io.mem_debug_read_data.expect(3.U)
+    }
+  }
+}