implemented subwf Instruction

Co-authored-by: Darkress <30271678+DarkressX@users.noreply.github.com>
Reviewed-on: darkress/pic16f84-sim#21

de/darkress/pic16f84sim/Main.java

@@ -12,14 +12,12 @@ class Main
     public static void main(String[] args) {
 
         ArrayList<Command> program = new ArrayList<>();
-        Memory.workingRegister = 0xAA;
-        int input1 = 0x2FFF;
-        program.add(CommandDecoder.decode(input1));
-
-        Memory.setPCLATH(0xFF);
-        program.get(0).execute();
-
-        //ProgramCounter.incPC();
-
+        Memory.workingRegister = 0x01;
+        Memory.setRegister(0x14, 0x01); //240 << 224
+        program.add(CommandDecoder.decode(0x0294));
+        for(int i = 0; i < program.size(); i++)
+        {
+            program.get(ProgramCounter.getPc()).execute();
+        }
     }
 }

de/darkress/pic16f84sim/commands/Addlw.java

@@ -3,7 +3,7 @@ package de.darkress.pic16f84sim.commands;
 import de.darkress.pic16f84sim.microcontroller.Memory;
 import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
 
-public class Addlw extends CommandUtils implements Command
+public class Addlw extends LiteralCommandUtils implements Command
 {
     private final int literal;
 

de/darkress/pic16f84sim/commands/Addwf.java

@@ -0,0 +1,29 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Addwf extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Addwf(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = checkDestinationBit(input);
+    }
+
+    @Override
+    public void execute()
+    {
+        int result = Memory.getRegister(address) + Memory.workingRegister;
+
+        checkZeroBit(result);
+        checkCarryBit(result);
+        checkDigitCarryBit(address);
+
+        writeToDestination(destinationBit, address, result);
+        ProgramCounter.incPC();
+    }
+}

de/darkress/pic16f84sim/commands/Andlw.java

@@ -2,7 +2,7 @@ package de.darkress.pic16f84sim.commands;
 
 import de.darkress.pic16f84sim.microcontroller.Memory;
 
-public class Andlw extends CommandUtils implements Command
+public class Andlw extends LiteralCommandUtils implements Command
 {
     private final int literal;
 

de/darkress/pic16f84sim/commands/Andwf.java

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

@@ -0,0 +1,18 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Clrw extends FileRegisterCommandUtils implements Command
+{
+    @Override
+    public void execute()
+    {
+        final int result = 0;
+
+        checkZeroBit(result);
+
+        Memory.workingRegister = result;
+        ProgramCounter.incPC();
+    }
+}

de/darkress/pic16f84sim/commands/Comf.java

@@ -0,0 +1,27 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Comf extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Comf(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = checkDestinationBit(input);
+    }
+
+    @Override
+    public void execute()
+    {
+        int result = 255 - Memory.getRegister(address); // Get inverse of 8Bit value
+
+        checkZeroBit(result);
+
+        writeToDestination(destinationBit, address, result);
+        ProgramCounter.incPC();
+    }
+}

de/darkress/pic16f84sim/commands/Decf.java

@@ -0,0 +1,27 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Decf extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Decf(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = checkDestinationBit(input);
+    }
+
+    @Override
+    public void execute()
+    {
+        int result = Memory.getRegister(address) + 255; // Allow underflow
+
+        checkZeroBit(result);
+
+        writeToDestination(destinationBit, address, result % 256); // Catch underflow
+        ProgramCounter.incPC();
+    }
+}

de/darkress/pic16f84sim/commands/Decfsz.java

@@ -0,0 +1,33 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Decfsz extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Decfsz(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = checkDestinationBit(input);
+    }
+
+    @Override
+    public void execute()
+    {
+        int result = Memory.getRegister(address) + 255; // Allow underflow
+
+        checkZeroBit(result);
+
+        writeToDestination(destinationBit, address, result % 256); // Catch underflow
+
+        if((result % 256) == 0)
+        {
+            Nop nop = new Nop();
+            nop.execute();
+        }
+        ProgramCounter.incPC();
+    }
+}

de/darkress/pic16f84sim/commands/FileRegisterCommandUtils.java

@@ -0,0 +1,51 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+
+public class FileRegisterCommandUtils
+{
+    protected void checkZeroBit(int result)
+    {
+        if((result % 256) == 0){
+            Memory.setZeroBit();
+        } else{
+            Memory.clearZeroBit();
+        }
+    }
+
+    protected void checkCarryBit(int result)
+    {
+        if(result > 255){
+            Memory.setCarryBit();
+        } else{
+            Memory.clearCarryBit();
+        }
+    }
+
+    protected void checkDigitCarryBit(int address)
+    {
+        int literal = Memory.getRegister(address);
+        if(((Memory.workingRegister & 0x0F) + (literal & 0x0F)) > 15){
+            Memory.setDigitCarryBit();
+        } else{
+            Memory.clearDigitCarryBit();
+        }
+    }
+
+    protected void writeToDestination(boolean destinationBit, int fileAddress, int result)
+    {
+        if(destinationBit)
+        {
+            //Store in FileRegister
+            Memory.setRegister(fileAddress, result);
+        } else {
+            //Store in WRegister
+            Memory.workingRegister = result;
+        }
+    }
+
+    protected boolean checkDestinationBit(int input)
+    {
+        return (input & 0x0080) == 0x0080;
+    }
+}

de/darkress/pic16f84sim/commands/Goto.java

@@ -1,9 +1,8 @@
 package de.darkress.pic16f84sim.commands;
 
-import de.darkress.pic16f84sim.microcontroller.Memory;
 import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
 
-public class Goto extends CommandUtils implements Command
+public class Goto extends LiteralCommandUtils implements Command
 {
     private final int literal;
 
@@ -15,6 +14,6 @@ public class Goto extends CommandUtils implements Command
     @Override
     public void execute()
     {
-        ProgramCounter.setPcForGotoCall(literal);
+        ProgramCounter.setPcFrom11BitLiteral(literal);
     }
 }

de/darkress/pic16f84sim/commands/Incf.java

@@ -0,0 +1,27 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Incf extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Incf(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = checkDestinationBit(input);
+    }
+
+    @Override
+    public void execute()
+    {
+        int result = Memory.getRegister(address) + 1; // Allow underflow
+
+        checkZeroBit(result);
+
+        writeToDestination(destinationBit, address, result % 256); // Catch underflow
+        ProgramCounter.incPC();
+    }
+}

de/darkress/pic16f84sim/commands/Incfsz.java

@@ -0,0 +1,33 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Incfsz extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Incfsz(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = checkDestinationBit(input);
+    }
+
+    @Override
+    public void execute()
+    {
+        int result = Memory.getRegister(address) + 1;
+
+        checkZeroBit(result);
+
+        writeToDestination(destinationBit, address, result % 256);
+
+        if((result % 256) == 0)
+        {
+            Nop nop = new Nop();
+            nop.execute();
+        }
+        ProgramCounter.incPC();
+    }
+}

de/darkress/pic16f84sim/commands/Iorlw.java

@@ -2,7 +2,7 @@ package de.darkress.pic16f84sim.commands;
 
 import de.darkress.pic16f84sim.microcontroller.Memory;
 
-public class Iorlw extends CommandUtils implements Command
+public class Iorlw extends LiteralCommandUtils implements Command
 {
     private final int literal;
 

de/darkress/pic16f84sim/commands/Iorwf.java

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

de/darkress/pic16f84sim/commands/LiteralCommandUtils.java

@@ -2,7 +2,7 @@ package de.darkress.pic16f84sim.commands;
 
 import de.darkress.pic16f84sim.microcontroller.Memory;
 
-public class CommandUtils
+public class LiteralCommandUtils
 {
     protected void checkZeroBit(int result)
     {

de/darkress/pic16f84sim/commands/Movf.java

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

de/darkress/pic16f84sim/commands/Movlw.java

@@ -1,8 +1,9 @@
 package de.darkress.pic16f84sim.commands;
 
 import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
 
-public class Movlw extends CommandUtils implements Command
+public class Movlw extends LiteralCommandUtils implements Command
 {
     private final int literal;
 
@@ -15,5 +16,6 @@ public class Movlw extends CommandUtils implements Command
     public void execute()
     {
         Memory.workingRegister = literal;
+        ProgramCounter.incPC();
     }
 }

de/darkress/pic16f84sim/commands/Movwf.java

@@ -0,0 +1,25 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.Memory;
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Movwf extends FileRegisterCommandUtils implements Command
+{
+    private final int address;
+    private final boolean destinationBit;
+
+    public Movwf(int input)
+    {
+        address = input & 0x007F;
+        destinationBit = true;
+    }
+
+    @Override
+    public void execute()
+    {
+        int result = Memory.workingRegister;
+
+        writeToDestination(destinationBit, address, result);
+        ProgramCounter.incPC();
+    }
+}

de/darkress/pic16f84sim/commands/Nop.java

@@ -0,0 +1,14 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+
+public class Nop extends LiteralCommandUtils implements Command
+{
+
+    @Override
+    public void execute()
+    {
+        // Do nothing, just increment the PC
+        ProgramCounter.incPC();
+    }
+}

de/darkress/pic16f84sim/commands/Retlw.java

@@ -0,0 +1,22 @@
+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 LiteralCommandUtils implements Command
+{
+    private final int literal;
+
+    public Retlw(int input)
+    {
+        literal = input & 0x00FF;
+    }
+
+    @Override
+    public void execute()
+    {
+        Memory.workingRegister = literal;
+        ProgramCounter.setPcFromStack(Stack.pop());
+    }
+}

de/darkress/pic16f84sim/commands/Return.java

@@ -0,0 +1,13 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+import de.darkress.pic16f84sim.microcontroller.Stack;
+
+public class Return extends LiteralCommandUtils implements Command
+{
+    @Override
+    public void execute()
+    {
+        ProgramCounter.setPcFromStack(Stack.pop());
+    }
+}

de/darkress/pic16f84sim/commands/Rlf.java

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

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();
+    }
+}

de/darkress/pic16f84sim/commands/Sublw.java

@@ -2,7 +2,7 @@ package de.darkress.pic16f84sim.commands;
 
 import de.darkress.pic16f84sim.microcontroller.Memory;
 
-public class Sublw extends CommandUtils implements Command
+public class Sublw extends LiteralCommandUtils implements Command
 {
     private final int literal;
 

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();
+    }
+}

de/darkress/pic16f84sim/commands/Xorlw.java

@@ -2,7 +2,7 @@ package de.darkress.pic16f84sim.commands;
 
 import de.darkress.pic16f84sim.microcontroller.Memory;
 
-public class Xorlw extends CommandUtils implements Command
+public class Xorlw extends LiteralCommandUtils implements Command
 {
     private final int literal;
 

de/darkress/pic16f84sim/decoder/CommandDecoder.java

@@ -9,41 +9,29 @@ public class CommandDecoder
         switch(input & 0x3F00)
         {
             case 0x700:
-                //addwf();
-                break;
+                return new Addwf(input);
             case 0x500:
-                //andwf();
-                break;
+                return new Andwf(input);
             case 0x900:
-                //comf();
-                break;
+                return new Comf(input);
             case 0x300:
-                //decf();
-                break;
+                return new Decf(input);
             case 0xB00:
-                //decfsz();
-                break;
+                return new Decfsz(input);
             case 0xA00:
-                //incf();
-                break;
+                return new Incf(input);
             case 0xF00:
-                //incfsz();
-                break;
+                return new Incfsz(input);
             case 0x400:
-                //iorwf();
-                break;
+                return new Iorwf(input);
             case 0x800:
-                //movf();
-                break;
+                return new Movf(input);
             case 0xD00:
-                //rlf();
-                break;
+                return new Rlf(input);
             case 0xC00:
-                //rrf();
-                break;
+                return new Rrf(input);
             case 0x200:
-                //subwf();
-                break;
+                return new Subwf(input);
             case 0xE00:
                 //swapf();
                 break;
@@ -61,14 +49,11 @@ public class CommandDecoder
         switch(input & 0x3F80)
         {
             case 0x180:
-                //clrf();
-                break;
+                return new Clrf(input);
             case 0x100:
-                //clrw();
-                break;
+                return new Clrw();
             case 0x80:
-                //movwf();
-                break;
+                return new Movwf(input);
         }
 
         switch(input & 0x3C00)
@@ -100,8 +85,7 @@ public class CommandDecoder
         switch(input & 0x3800)
         {
             case 0x2000:
-                //call();
-                break;
+                return new Call(input);
             case 0x2800:
                 return new Goto(input);
         }
@@ -111,13 +95,12 @@ public class CommandDecoder
             case 0x3000:
                 return new Movlw(input);
             case 0x3400:
-                //retlw();
-                break;
+                return new Retlw(input);
         }
 
         if ((input | 0x0060) == 0x0060)
         {
-            //nop();
+            return new Nop();
         }
 
         if (input == 0x0064)
@@ -132,8 +115,7 @@ 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

@@ -59,6 +59,10 @@ public class Memory
         }
         memory[address] = data;
         memory[address + 128] = data; //Ensure data is written to both banks to simulate mapping
+        if(address == 0x2) //Check if PCL is destination
+        {
+            ProgramCounter.loadPc();
+        }
     }
 
     private static int getDataFromIndirectAddress(int address)
@@ -75,6 +79,10 @@ public class Memory
         }
         memory[address % 128] = data; // else: Registers.Registers which are mapped
         memory[address % 128 + 128] = data; //Ensure data is written to both banks to simulate mapping
+        if(address == 0x2) //Check if PCL is destination
+        {
+            ProgramCounter.loadPc();
+        }
     }
 
     private static int getRegisterBank()
@@ -145,9 +153,13 @@ public class Memory
         memory[0x03] &= 0xFD;
     }
 
-    public static boolean getCarryBit()
+    public static int getCarryBit()
     {
-        return (memory[0x03] & 0x01) == 0x01;
+        if((memory[0x03] & 0x01) == 0x01)
+        {
+            return 1;
+        }
+        else return 0;
     }
 
     public static void setCarryBit()

de/darkress/pic16f84sim/microcontroller/ProgramCounter.java

@@ -11,7 +11,7 @@ public class ProgramCounter
         return pc;
     }
 
-    public static void setPcForGotoCall(int data)
+    public static void setPcFrom11BitLiteral(int data)
     {
         int pcl = data & 0x00FF;
         int pch = Memory.getPCLATH();
@@ -20,19 +20,20 @@ public class ProgramCounter
         pc = (pch) + pcl;
     }
 
+    public static void setPcFromStack(int stack)
+    {
+        pc = stack;
+        Memory.setPCL(pc & 0x00FF);
+    }
+
+    public static void loadPc()
+    {
+        pc = (Memory.getPCLATH() <<8) + Memory.getPCL();
+    }
+
     public static void incPC() //is called after every instruction execution
     {
-        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;
+        pc++;
+        Memory.setPCL(pc & 0x00FF);
     }
 }

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()