Program counter

Author: outercloudstudio

src/main/scala/main/Alu.scala

@@ -8,7 +8,7 @@ object AluOperation extends ChiselEnum {
 
 class Alu extends Module {
   val io = IO(new Bundle {
-    val enable = Input(Bool());
+    val execute = Input(Bool());
 
     val operation = Input(AluOperation());
     val compare = Input(Bool());
@@ -21,7 +21,7 @@ class Alu extends Module {
 
   io.output := 0.U;
 
-  when(io.enable) {
+  when(io.execute) {
     when(io.compare) {
       val gt = io.rs > io.rt;
       val eq = io.rs === io.rt;

src/main/scala/main/ProgramCounter.scala

@@ -0,0 +1,34 @@
+import chisel3._
+import chisel3.util._
+import _root_.circt.stage.ChiselStage
+
+class ProgramCounter extends Module {
+  val io = IO(new Bundle {
+    val store_nzp = Input(Bool());
+    val nzp = Input(UInt(3.W));
+    
+    val update = Input(Bool());
+    val branch = Input(Bool());
+    val jump_location = Input(UInt(8.W));
+    val target_nzp = Input(UInt(3.W));
+  
+    val program_counter = Output(UInt(8.W)); 
+  })
+
+  val nzp = RegInit(0.U(3.W));
+
+  val program_counter = RegInit(0.U(8.W));
+  io.program_counter := program_counter;
+
+  when(io.store_nzp) {
+    nzp := io.nzp;
+  }
+
+  when(io.update) {
+    when(io.branch && (nzp & io.target_nzp) =/= 0.U) {
+      program_counter := io.jump_location;
+    }.otherwise {
+      program_counter := program_counter + 1.U;
+    }
+  }
+}

src/test/scala/main/AluTest.scala

@@ -5,7 +5,7 @@ import org.scalatest.flatspec.AnyFlatSpec
 class AluTest extends AnyFlatSpec with ChiselScalatestTester {
   "Alu Add" should "work" in {
     test(new Alu) { dut =>
-      dut.io.enable.poke(true.B);
+      dut.io.execute.poke(true.B);
       dut.io.operation.poke(AluOperation.Add);
       dut.io.compare.poke(false.B);
       dut.io.rs.poke(2.U);

src/test/scala/main/ProgramCounterTest.scala

@@ -0,0 +1,51 @@
+import chisel3._
+import chiseltest._
+import org.scalatest.flatspec.AnyFlatSpec
+
+class ProgramCounterTest extends AnyFlatSpec with ChiselScalatestTester {
+  "Program Counter Increment" should "work" in {
+    test(new ProgramCounter) { dut =>
+      dut.io.update.poke(true.B);
+
+      dut.clock.step(1);
+
+      dut.io.program_counter.expect(1.U);
+    }
+  }
+
+  "Program Counter Jump" should "work" in {
+    test(new ProgramCounter) { dut =>
+      dut.io.store_nzp.poke(true.B);
+      dut.io.nzp.poke(1.U);
+
+      dut.clock.step(1);
+
+      dut.io.update.poke(true.B);
+      dut.io.branch.poke(true.B);
+      dut.io.jump_location.poke(8.U);
+      dut.io.target_nzp.poke(1.U);
+
+      dut.clock.step(1);
+
+      dut.io.program_counter.expect(8.U);
+    }
+  }
+
+  "Program Counter Jump Fail" should "work" in {
+    test(new ProgramCounter) { dut =>
+      dut.io.store_nzp.poke(true.B);
+      dut.io.nzp.poke(1.U);
+
+      dut.clock.step(1);
+
+      dut.io.update.poke(true.B);
+      dut.io.branch.poke(true.B);
+      dut.io.jump_location.poke(8.U);
+      dut.io.target_nzp.poke(2.U);
+
+      dut.clock.step(1);
+
+      dut.io.program_counter.expect(1.U);
+    }
+  }
+}