implemented subwf Instruction

de/darkress/pic16f84sim/commands/Subwf.java

@@ -0,0 +1,49 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Subwf extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Subwf(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = checkDestinationBit(input);
+    }
+
+    @Override
+    protected void checkCarryBit(int result)
+    {
+        if(result <= 255){
+            Memory.clearCarryBit();
+        } else{
+            Memory.setCarryBit();
+        }
+    }
+
+    @Override
+    protected void checkDigitCarryBit(int literal)
+    {
+        if(((literal & 0x0F) - (Memory.workingRegister & 0x0F)) < 0){
+            Memory.clearDigitCarryBit();
+        } else{
+            Memory.setDigitCarryBit();
+        }
+    }
+
+    @Override
+    public void execute()
+    {
+        int result = Memory.getRegister(address) - Memory.workingRegister + 256;
+
+        checkZeroBit(result);
+        checkCarryBit(result);
+        checkDigitCarryBit(Memory.getRegister(address));
+
+        writeToDestination(destinationBit, address, result % 256);
+        ProgramCounter.incPC();
+    }
+}