implemented Clrf Instruction

Co-authored-by: darkress <github@darkress.xyz>
Reviewed-on: darkress/pic16f84-sim#15

de/darkress/pic16f84sim/Main.java

@@ -12,8 +12,8 @@ class Main
     public static void main(String[] args) {
 
         ArrayList<Command> program = new ArrayList<>();
-        Memory.workingRegister = 0x10;
-        program.add(CommandDecoder.decode(0x123)); //Write 0x11 to W
+        Memory.setRegister(0x14, 0xFF);
+        program.add(CommandDecoder.decode(0x0194));
         for(int i = 0; i < program.size(); i++)
         {
             program.get(ProgramCounter.getPc()).execute();

de/darkress/pic16f84sim/commands/Clrf.java

@@ -0,0 +1,27 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Clrf extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Clrf(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = true;
+    }
+
+    @Override
+    public void execute()
+    {
+        final int result = 0;
+
+        checkZeroBit(result);
+
+        writeToDestination(destinationBit, address, result);
+        ProgramCounter.incPC();
+    }
+}

de/darkress/pic16f84sim/decoder/CommandDecoder.java

@@ -54,8 +54,7 @@ public class CommandDecoder
         switch(input & 0x3F80)
         {
             case 0x180:
-                //clrf();
-                break;
+                return new Clrf(input);
             case 0x100:
                 return new Clrw();
             case 0x80: