Simplify NOP and bubble logic.

src/main/scala/IF.scala

@@ -8,7 +8,7 @@ class InstructionFetch extends MultiIOModule {
   val testHarness = IO(
     new Bundle {
       val IMEMsetup = Input(new IMEMsetupSignals)
-      val PC = Output(UInt())
+      val PC        = Output(UInt())
     }
   )
 
@@ -46,21 +46,11 @@ class InstructionFetch extends MultiIOModule {
   instruction := IMEM.io.instruction.asTypeOf(new Instruction)
 
 
-
-
   /**
-    * Setup.
+    * Setup. You should not change this code.
-    * 
-    * When you have added an instruction signal to this module you
-    * should ensure that it is set to NOP during program loading.
-    * 
-    * If not you will end up issuing instructions during program load
-    * which will start executing before memory, registers and programs
-    * are fully loaded.
     */
   when(testHarness.IMEMsetup.setup) {
     PC := 0.U
-    // TODO: You should probably set the instruction to Instruction.NOP here.
+    instruction := Instruction.NOP
-    // throw new Exception("Just making sure you're seeing the line above.\nYou can delete this exception now, it's found at line 64 at IF.scala")
   }
 }

src/main/scala/ToplevelSignals.scala

@@ -22,14 +22,17 @@ class Instruction extends Bundle(){
   def immediateJType = Cat(instruction(31), instruction(19, 12), instruction(20), instruction(30, 25), instruction(24, 21), 0.U(1.W)).asSInt
   def immediateZType = instruction(19, 15).zext
 
+  def bubble(): Instruction = {
+    val bubbled = Wire(new Instruction)
+    bubbled.instruction := instruction
+    bubbled.instruction(6, 0) := BitPat.bitPatToUInt(BitPat("b0010011"))
+    bubbled
+  }
 }
 object Instruction {
-  def bubble(i: Instruction) =
+  def NOP: Instruction = {
-    i.opcode := BitPat.bitPatToUInt(BitPat("b0010011"))
-
-  def default: Instruction = {
     val w = Wire(new Instruction)
-    w.instruction := 0.U
+    w.instruction := BitPat.bitPatToUInt(BitPat("b00000000000000000000000000010011"))
     w
   }
 }