implemented Retlw instruction

Co-authored-by: Darkress <30271678+DarkressX@users.noreply.github.com>
Reviewed-on: darkress/pic16f84-sim#4

de/darkress/pic16f84sim/Main.java

@@ -12,13 +12,14 @@ class Main
     public static void main(String[] args) {
 
         ArrayList<Command> program = new ArrayList<>();
-        Memory.workingRegister = 0xAA;
         int input1 = 0x27FF;
-        program.add(CommandDecoder.decode(input1));
-
-        Memory.setPCLATH(0xFF);
-        program.get(0).execute();
-
-        //ProgramCounter.incPC();
+        program.add(CommandDecoder.decode(0x3011));
+        program.add(CommandDecoder.decode(0x2003));
+        program.add(CommandDecoder.decode(0x3022));
+        program.add(CommandDecoder.decode(0x0008));
+        while(true)
+        {
+            program.get(ProgramCounter.getPc()).execute();
+        }
     }
 }

de/darkress/pic16f84sim/commands/Retlw.java

@@ -0,0 +1,24 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+import de.darkress.pic16f84sim.microcontroller.Stack;
+
+public class Retlw extends CommandUtils implements Command
+{
+    private final int literal;
+
+    public Retlw(int input)
+    {
+        literal = input & 0x00FF;
+    }
+
+    @Override
+    public void execute()
+    {
+        Memory.workingRegister = literal;
+        ProgramCounter.setPcFrom11BitLiteral(Stack.pop());
+        //TODO: This may need some rework since it does not really load all 13 Bit into the PC. Only 8 Bit are
+        // effectively set
+    }
+}

de/darkress/pic16f84sim/commands/Return.java

@@ -0,0 +1,15 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+import de.darkress.pic16f84sim.microcontroller.Stack;
+
+public class Return extends CommandUtils implements Command
+{
+    @Override
+    public void execute()
+    {
+        ProgramCounter.setPcFrom11BitLiteral(Stack.pop());
+        //TODO: This may need some rework since it does not really load all 13 Bit into the PC. Only 8 Bit are
+        // effectively set
+    }
+}

de/darkress/pic16f84sim/decoder/CommandDecoder.java

@@ -110,8 +110,7 @@ public class CommandDecoder
             case 0x3000:
                 return new Movlw(input);
             case 0x3400:
-                //retlw();
-                break;
+                return new Retlw(input);
         }
 
         if ((input | 0x0060) == 0x0060)
@@ -131,8 +130,7 @@ public class CommandDecoder
 
         if (input == 0x0008)
         {
-            //return();
-            //This is the function name. Do not mistake this for a normal return!
+            return new Return();
         }
 
         if (input == 0x0063)

de/darkress/pic16f84sim/microcontroller/Stack.java

@@ -14,9 +14,8 @@ public class Stack
 
     public static int pop()
     {
-        int tmp = stack[stackPointer];
         pointPrevious();
-        return tmp;
+        return stack[stackPointer];
     }
 
     public static int peek()