JSR and RTS implementation

//=========
//---------
//   JSR
//---------
//=========

//Switch case for JSR
                case 0x20:
                    cv.M = sr.AM_Absolute();     //Returns a 16-bit address after PC (used to set PC to target location)
                    sr.OP_JSR(cv.M);    //Give it to OP_JSR

                    cv.cycle -= 6;
                    break;

//Absolute addressing mode
    public ushort AM_Absolute()
    {
        ushort result = cv.memory[cv.PC + 2];    //Read high byte for address
        result = (ushort)(result << 8);    //Shift to right position
        result += cv.memory[cv.PC + 1];    //Add low byte

        return result;
    }

//JSR instruction
    public void OP_JSR(ushort addr)
    {
        ushort temp = (ushort)(cv.PC + 2);     //Get return address
        PushWord(temp);    //Push it to stack
        cv.PC = addr;     //Set PC to target location
    }

//Push word to stack
    public void PushWord(ushort w)
    {
        byte hi = (byte)((w & 0xFF00) >> 8);    //Get high byte and shift it to right place
        cv.memory[0x0100 + cv.S] = hi;    //Store value to stack
        cv.S--;    //Decrement stack pointer

        byte lo = (byte)(w & 0x00FF);    //Get low byte and shift it to right place
        cv.memory[0x0100 + cv.S] = lo;    //Store value to stack
        cv.S--;    //Decrement stack pointer
    }



//=========
//---------
//   RTS
//---------
//=========

//Switch case for RTS
                case 0x60:
                    sr.OP_RTS();    //Call OP_RTS

                    cv.cycle -= 6;
                    break;

//RTS instruction
    public void OP_RTS()
    {
        byte lo = PullStack();    //Pull low byte from stack
        byte hi = PullStack();    //Pull high byte from stack
        ushort result = CombineBytes(lo, hi);    //Combine them to a word
        result++;    //Increment result to get to next instruction
        cv.PC = result;    //Set PC to return address
    }

//Pull a byte from stack
    public byte PullStack()
    {
        byte b = cv.memory[0x0100 + cv.S];    //Read value from stack
        cv.S++;    //Increment stack pointer

        return b;
    }

//Combine bytes to word
    public ushort CombineBytes(byte lo, byte hi)
    {
        ushort result;

        result = hi;    //Set high byte
        result = (ushort)(result << 8);    //Shift it to right place
        result += lo;    //Add low byte

        return result;
    }