implemented Retlw instruction

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

de/darkress/pic16f84sim/Main.java

@@ -3,16 +3,23 @@ package de.darkress.pic16f84sim;
 import de.darkress.pic16f84sim.commands.Command;
 import de.darkress.pic16f84sim.decoder.CommandDecoder;
 import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
 import java.util.ArrayList;
 
 class Main
 {
     public static void main(String[] args) {
-        ArrayList<Command> program = new ArrayList<>();
-        Memory.workingRegister = 0xAA;
-        int input1 = 0x3AFF;
-        program.add(CommandDecoder.decode(input1));
-        program.get(0).execute();
 
+        ArrayList<Command> program = new ArrayList<>();
+        int input1 = 0x27FF;
+        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/Addlw.java

@@ -1,6 +1,7 @@
 package de.darkress.pic16f84sim.commands;
 
 import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
 
 public class Addlw extends CommandUtils implements Command
 {
@@ -21,5 +22,6 @@ public class Addlw extends CommandUtils implements Command
         checkDigitCarryBit(literal);
 
         Memory.workingRegister = result % 256;
+        ProgramCounter.incPC();
     }
 }

de/darkress/pic16f84sim/commands/Call.java

@@ -0,0 +1,21 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+import de.darkress.pic16f84sim.microcontroller.Stack;
+
+public class Call extends CommandUtils implements Command
+{
+    private final int literal;
+
+    public Call(int input)
+    {
+        literal = input & 0x07FF;
+    }
+
+    @Override
+    public void execute()
+    {
+        Stack.push(ProgramCounter.getPc() + 1);
+        ProgramCounter.setPcFrom11BitLiteral(literal);
+    }
+}

de/darkress/pic16f84sim/commands/Goto.java

@@ -0,0 +1,19 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Goto extends CommandUtils implements Command
+{
+    private final int literal;
+
+    public Goto(int input)
+    {
+        literal = input & 0x07FF;
+    }
+
+    @Override
+    public void execute()
+    {
+        ProgramCounter.setPcFrom11BitLiteral(literal);
+    }
+}

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

@@ -100,11 +100,9 @@ public class CommandDecoder
         switch(input & 0x3800)
         {
             case 0x2000:
-                //call();
-                break;
+                return new Call(input);
             case 0x2800:
-                //goto();
-                break;
+                return new Goto(input);
         }
 
         switch(input & 0x3C00)
@@ -112,8 +110,7 @@ public class CommandDecoder
             case 0x3000:
                 return new Movlw(input);
             case 0x3400:
-                //retlw();
-                break;
+                return new Retlw(input);
         }
 
         if ((input | 0x0060) == 0x0060)
@@ -133,8 +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/Memory.java

@@ -91,6 +91,28 @@ public class Memory
         return memory[0x4];
     }
 
+    public static int getPCL()
+    {
+        return memory[0x2];
+    }
+
+    public static void setPCL(int data)
+    {
+        memory[0x2] = data;
+        memory[0x82] = data;
+    }
+
+    public static int getPCLATH()
+    {
+        return memory[0xA] & 0x1F;
+    }
+
+    public static void setPCLATH(int data)
+    {
+        memory[0xA] = data & 0x1F;
+        memory[0x8A] = data & 0x1F;
+    }
+
     public static boolean getZeroBit()
     {
         return (memory[0x03] & 0x04) == 0x04;
@@ -99,6 +121,7 @@ public class Memory
     public static void setZeroBit()
     {
         memory[0x03] |= 0x04;
+        memory[0x83] |= 0x04;
     }
 
     public static void clearZeroBit()
@@ -114,6 +137,7 @@ public class Memory
     public static void setDigitCarryBit()
     {
         memory[0x03] |= 0x02;
+        memory[0x83] |= 0x02;
     }
 
     public static void clearDigitCarryBit()
@@ -129,6 +153,7 @@ public class Memory
     public static void setCarryBit()
     {
         memory[0x03] |= 0x01;
+        memory[0x83] |= 0x01;
     }
 
     public static void clearCarryBit()

de/darkress/pic16f84sim/microcontroller/ProgramCounter.java

@@ -4,20 +4,35 @@ public class ProgramCounter
 
     //This class is not actual part of the µC. It is a storage for the current value of the PC
 {
-    private static int PC = 0;
+    private static int pc = 0;
 
-    public static int getPC()
+    public static int getPc()
     {
-        return PC;
+        return pc;
     }
 
-    public static void setPC(int PC)
+    public static void setPcFrom11BitLiteral(int data)
     {
-        ProgramCounter.PC = PC;
+        int pcl = data & 0x00FF;
+        int pch = Memory.getPCLATH();
+        pch = ((pch & 0xF8) <<8) + (data & 0x700);
+        Memory.setPCL(pcl);
+        pc = (pch) + pcl;
     }
 
-    public static void incPC()
+    public static void incPC() //is called after every instruction execution
     {
-        PC++;
+        int pcl = Memory.getPCL();
+        int pclath = Memory.getPCLATH();
+        if(pcl == 0xFF)
+        {
+            pclath++;
+            pcl = 0;
+        } else {
+            pcl++;
+        }
+        Memory.setPCL(pcl);
+        Memory.setPCLATH(pclath);
+        pc = (pclath <<8) + pcl;
     }
 }

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()