implemented Rrf Instruction

de/darkress/pic16f84sim/commands/Rrf.java

@@ -0,0 +1,35 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Rrf extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Rrf(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = checkDestinationBit(input);
+    }
+
+    @Override
+    public void execute()
+    {
+        int register = Memory.getRegister(address);
+        int newCarry = register & 0x01;
+        int oldCarry = Memory.getCarryBit();
+        register = (oldCarry << 7) + (register >>1);
+
+        if(newCarry == 1)
+        {
+            Memory.setCarryBit();
+        } else if(newCarry == 0){
+            Memory.clearCarryBit();
+        }
+
+        writeToDestination(destinationBit, address, register);
+        ProgramCounter.incPC();
+    }
+}