cpu.js

/*
JSNES, based on Jamie Sanders' vNES
Copyright (C) 2010 Ben Firshman

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

JSNES.CPU = function(nes) {
    this.nes = nes;
    
    // Keep Chrome happy
    this.mem = null;
    this.REG_ACC = null;
    this.REG_X = null;
    this.REG_Y = null;
    this.REG_SP = null;
    this.REG_PC = null;
    this.REG_PC_NEW = null;
    this.REG_STATUS = null;
    this.F_CARRY = null;
    this.F_DECIMAL = null;
    this.F_INTERRUPT = null;
    this.F_INTERRUPT_NEW = null;
    this.F_OVERFLOW = null;
    this.F_SIGN = null;
    this.F_ZERO = null;
    this.F_NOTUSED = null;
    this.F_NOTUSED_NEW = null;
    this.F_BRK = null;
    this.F_BRK_NEW = null;
    this.opdata = null;
    this.cyclesToHalt = null;
    this.crash = null;
    this.irqRequested = null;
    this.irqType = null;
    
    this.reset();
};

JSNES.CPU.prototype = {
    // IRQ Types
    IRQ_NORMAL: 0,
    IRQ_NMI: 1,
    IRQ_RESET: 2,
    
    reset: function() {
        // Main memory 
        this.mem = new Array(0x10000);
        
        for (var i=0; i < 0x2000; i++) {
            this.mem[i] = 0xFF;
        }
        for (var p=0; p < 4; p++) {
            var i = p*0x800;
            this.mem[i+0x008] = 0xF7;
            this.mem[i+0x009] = 0xEF;
            this.mem[i+0x00A] = 0xDF;
            this.mem[i+0x00F] = 0xBF;
        }
        for (var i=0x2001; i < this.mem.length; i++) {
            this.mem[i] = 0;
        }
        
        // CPU Registers:
        this.REG_ACC = 0;
        this.REG_X = 0;
        this.REG_Y = 0;
        // Reset Stack pointer:
        this.REG_SP = 0x01FF;
        // Reset Program counter:
        this.REG_PC = 0x8000-1;
        this.REG_PC_NEW = 0x8000-1;
        // Reset Status register:
        this.REG_STATUS = 0x28;
        
        this.setStatus(0x28);
        
        // Set flags:
        this.F_CARRY = 0;
        this.F_DECIMAL = 0;
        this.F_INTERRUPT = 1;
        this.F_INTERRUPT_NEW = 1;
        this.F_OVERFLOW = 0;
        this.F_SIGN = 0;
        this.F_ZERO = 1;

        this.F_NOTUSED = 1;
        this.F_NOTUSED_NEW = 1;
        this.F_BRK = 1;
        this.F_BRK_NEW = 1;
        
        this.opdata = new JSNES.CPU.OpData().opdata;
        this.cyclesToHalt = 0;
        
        // Reset crash flag:
        this.crash = false;
        
        // Interrupt notification:
        this.irqRequested = false;
        this.irqType = null;

    },
    
    // Emulates a single CPU instruction, returns the number of cycles
    emulate: function() {
        var temp;
        var add;
        
        // Check interrupts:
        if(this.irqRequested){
            temp =
                (this.F_CARRY)|
                ((this.F_ZERO===0?1:0)<<1)|
                (this.F_INTERRUPT<<2)|
                (this.F_DECIMAL<<3)|
                (this.F_BRK<<4)|
                (this.F_NOTUSED<<5)|
                (this.F_OVERFLOW<<6)|
                (this.F_SIGN<<7);

            this.REG_PC_NEW = this.REG_PC;
            this.F_INTERRUPT_NEW = this.F_INTERRUPT;
            switch(this.irqType){
                case 0: {
                    // Normal IRQ:
                    if(this.F_INTERRUPT!=0){
                        ////System.out.println("Interrupt was masked.");
                        break;
                    }
                    this.doIrq(temp);
                    ////System.out.println("Did normal IRQ. I="+this.F_INTERRUPT);
                    break;
                }case 1:{
                    // NMI:
                    this.doNonMaskableInterrupt(temp);
                    break;

                }case 2:{
                    // Reset:
                    this.doResetInterrupt();
                    break;
                }
            }

            this.REG_PC = this.REG_PC_NEW;
            this.F_INTERRUPT = this.F_INTERRUPT_NEW;
            this.F_BRK = this.F_BRK_NEW;
            this.irqRequested = false;
        }

        var opinf = this.opdata[this.nes.mmap.load(this.REG_PC+1)];
        var cycleCount = (opinf>>24);
        var cycleAdd = 0;

        // Find address mode:
        var addrMode = (opinf >> 8) & 0xFF;

        // Increment PC by number of op bytes:
        var opaddr = this.REG_PC;
        this.REG_PC += ((opinf >> 16) & 0xFF);
        
        var addr = 0;
        switch(addrMode){
            case 0:{
                // Zero Page mode. Use the address given after the opcode, 
                // but without high byte.
                addr = this.load(opaddr+2);
                break;

            }case 1:{
                // Relative mode.
                addr = this.load(opaddr+2);
                if(addr<0x80){
                    addr += this.REG_PC;
                }else{
                    addr += this.REG_PC-256;
                }
                break;
            }case 2:{
                // Ignore. Address is implied in instruction.
                break;
            }case 3:{
                // Absolute mode. Use the two bytes following the opcode as 
                // an address.
                addr = this.load16bit(opaddr+2);
                break;
            }case 4:{
                // Accumulator mode. The address is in the accumulator 
                // register.
                addr = this.REG_ACC;
                break;
            }case 5:{
                // Immediate mode. The value is given after the opcode.
                addr = this.REG_PC;
                break;
            }case 6:{
                // Zero Page Indexed mode, X as index. Use the address given 
                // after the opcode, then add the
                // X register to it to get the final address.
                addr = (this.load(opaddr+2)+this.REG_X)&0xFF;
                break;
            }case 7:{
                // Zero Page Indexed mode, Y as index. Use the address given 
                // after the opcode, then add the
                // Y register to it to get the final address.
                addr = (this.load(opaddr+2)+this.REG_Y)&0xFF;
                break;
            }case 8:{
                // Absolute Indexed Mode, X as index. Same as zero page 
                // indexed, but with the high byte.
                addr = this.load16bit(opaddr+2);
                if((addr&0xFF00)!=((addr+this.REG_X)&0xFF00)){
                    cycleAdd = 1;
                }
                addr+=this.REG_X;
                break;
            }case 9:{
                // Absolute Indexed Mode, Y as index. Same as zero page 
                // indexed, but with the high byte.
                addr = this.load16bit(opaddr+2);
                if((addr&0xFF00)!=((addr+this.REG_Y)&0xFF00)){
                    cycleAdd = 1;
                }
                addr+=this.REG_Y;
                break;
            }case 10:{
                // Pre-indexed Indirect mode. Find the 16-bit address 
                // starting at the given location plus
                // the current X register. The value is the contents of that 
                // address.
                addr = this.load(opaddr+2);
                if((addr&0xFF00)!=((addr+this.REG_X)&0xFF00)){
                    cycleAdd = 1;
                }
                addr+=this.REG_X;
                addr&=0xFF;
                addr = this.load16bit(addr);
                break;
            }case 11:{
                // Post-indexed Indirect mode. Find the 16-bit address 
                // contained in the given location
                // (and the one following). Add to that address the contents 
                // of the Y register. Fetch the value
                // stored at that adress.
                addr = this.load16bit(this.load(opaddr+2));
                if((addr&0xFF00)!=((addr+this.REG_Y)&0xFF00)){
                    cycleAdd = 1;
                }
                addr+=this.REG_Y;
                break;
            }case 12:{
                // Indirect Absolute mode. Find the 16-bit address contained 
                // at the given location.
                addr = this.load16bit(opaddr+2);// Find op
                if(addr < 0x1FFF) {
                    addr = this.mem[addr] + (this.mem[(addr & 0xFF00) | (((addr & 0xFF) + 1) & 0xFF)] << 8);// Read from address given in op
                }
                else{
                    addr = this.nes.mmap.load(addr) + (this.nes.mmap.load((addr & 0xFF00) | (((addr & 0xFF) + 1) & 0xFF)) << 8);
                }
                break;

            }

        }
        // Wrap around for addresses above 0xFFFF:
        addr&=0xFFFF;

        // ----------------------------------------------------------------------------------------------------
        // Decode & execute instruction:
        // ----------------------------------------------------------------------------------------------------

        // This should be compiled to a jump table.
        switch(opinf&0xFF){
            case 0:{
                // *******
                // * ADC *
                // *******

                // Add with carry.
                temp = this.REG_ACC + this.load(addr) + this.F_CARRY;
                this.F_OVERFLOW = ((!(((this.REG_ACC ^ this.load(addr)) & 0x80)!=0) && (((this.REG_ACC ^ temp) & 0x80))!=0)?1:0);
                this.F_CARRY = (temp>255?1:0);
                this.F_SIGN = (temp>>7)&1;
                this.F_ZERO = temp&0xFF;
                this.REG_ACC = (temp&255);
                cycleCount+=cycleAdd;
                break;

            }case 1:{
                // *******
                // * AND *
                // *******

                // AND memory with accumulator.
                this.REG_ACC = this.REG_ACC & this.load(addr);
                this.F_SIGN = (this.REG_ACC>>7)&1;
                this.F_ZERO = this.REG_ACC;
                //this.REG_ACC = temp;
                if(addrMode!=11)cycleCount+=cycleAdd; // PostIdxInd = 11
                break;
            }case 2:{
                // *******
                // * ASL *
                // *******

                // Shift left one bit
                if(addrMode == 4){ // ADDR_ACC = 4

                    this.F_CARRY = (this.REG_ACC>>7)&1;
                    this.REG_ACC = (this.REG_ACC<<1)&255;
                    this.F_SIGN = (this.REG_ACC>>7)&1;
                    this.F_ZERO = this.REG_ACC;

                }else{

                    temp = this.load(addr);
                    this.F_CARRY = (temp>>7)&1;
                    temp = (temp<<1)&255;
                    this.F_SIGN = (temp>>7)&1;
                    this.F_ZERO = temp;
                    this.write(addr, temp);

                }
                break;

            }case 3:{

                // *******
                // * BCC *
                // *******

                // Branch on carry clear
                if(this.F_CARRY == 0){
                    cycleCount += ((opaddr&0xFF00)!=(addr&0xFF00)?2:1);
                    this.REG_PC = addr;
                }
                break;

            }case 4:{

                // *******
                // * BCS *
                // *******

                // Branch on carry set
                if(this.F_CARRY == 1){
                    cycleCount += ((opaddr&0xFF00)!=(addr&0xFF00)?2:1);
                    this.REG_PC = addr;
                }
                break;

            }case 5:{

                // *******
                // * BEQ *
                // *******

                // Branch on zero
                if(this.F_ZERO == 0){
                    cycleCount += ((opaddr&0xFF00)!=(addr&0xFF00)?2:1);
                    this.REG_PC = addr;
                }
                break;

            }case 6:{

                // *******
                // * BIT *
                // *******

                temp = this.load(addr);
                this.F_SIGN = (temp>>7)&1;
                this.F_OVERFLOW = (temp>>6)&1;
                temp &= this.REG_ACC;
                this.F_ZERO = temp;
                break;

            }case 7:{

                // *******
                // * BMI *
                // *******

                // Branch on negative result
                if(this.F_SIGN == 1){
                    cycleCount++;
                    this.REG_PC = addr;
                }
                break;

            }case 8:{

                // *******
                // * BNE *
                // *******

                // Branch on not zero
                if(this.F_ZERO != 0){
                    cycleCount += ((opaddr&0xFF00)!=(addr&0xFF00)?2:1);
                    this.REG_PC = addr;
                }
                break;

            }case 9:{

                // *******
                // * BPL *
                // *******

                // Branch on positive result
                if(this.F_SIGN == 0){
                    cycleCount += ((opaddr&0xFF00)!=(addr&0xFF00)?2:1);
                    this.REG_PC = addr;
                }
                break;

            }case 10:{

                // *******
                // * BRK *
                // *******

                this.REG_PC+=2;
                this.push((this.REG_PC>>8)&255);
                this.push(this.REG_PC&255);
                this.F_BRK = 1;

                this.push(
                    (this.F_CARRY)|
                    ((this.F_ZERO==0?1:0)<<1)|
                    (this.F_INTERRUPT<<2)|
                    (this.F_DECIMAL<<3)|
                    (this.F_BRK<<4)|
                    (this.F_NOTUSED<<5)|
                    (this.F_OVERFLOW<<6)|
                    (this.F_SIGN<<7)
                );

                this.F_INTERRUPT = 1;
                //this.REG_PC = load(0xFFFE) | (load(0xFFFF) << 8);
                this.REG_PC = this.load16bit(0xFFFE);
                this.REG_PC--;
                break;

            }case 11:{

                // *******
                // * BVC *
                // *******

                // Branch on overflow clear
                if(this.F_OVERFLOW == 0){
                    cycleCount += ((opaddr&0xFF00)!=(addr&0xFF00)?2:1);
                    this.REG_PC = addr;
                }
                break;

            }case 12:{

                // *******
                // * BVS *
                // *******

                // Branch on overflow set
                if(this.F_OVERFLOW == 1){
                    cycleCount += ((opaddr&0xFF00)!=(addr&0xFF00)?2:1);
                    this.REG_PC = addr;
                }
                break;

            }case 13:{

                // *******
                // * CLC *
                // *******

                // Clear carry flag
                this.F_CARRY = 0;
                break;

            }case 14:{

                // *******
                // * CLD *
                // *******

                // Clear decimal flag
                this.F_DECIMAL = 0;
                break;

            }case 15:{

                // *******
                // * CLI *
                // *******

                // Clear interrupt flag
                this.F_INTERRUPT = 0;
                break;

            }case 16:{

                // *******
                // * CLV *
                // *******

                // Clear overflow flag
                this.F_OVERFLOW = 0;
                break;

            }case 17:{

                // *******
                // * CMP *
                // *******

                // Compare memory and accumulator:
                temp = this.REG_ACC - this.load(addr);
                this.F_CARRY = (temp>=0?1:0);
                this.F_SIGN = (temp>>7)&1;
                this.F_ZERO = temp&0xFF;
                cycleCount+=cycleAdd;
                break;

            }case 18:{

                // *******
                // * CPX *
                // *******

                // Compare memory and index X:
                temp = this.REG_X - this.load(addr);
                this.F_CARRY = (temp>=0?1:0);
                this.F_SIGN = (temp>>7)&1;
                this.F_ZERO = temp&0xFF;
                break;

            }case 19:{

                // *******
                // * CPY *
                // *******

                // Compare memory and index Y:
                temp = this.REG_Y - this.load(addr);
                this.F_CARRY = (temp>=0?1:0);
                this.F_SIGN = (temp>>7)&1;
                this.F_ZERO = temp&0xFF;
                break;

            }case 20:{

                // *******
                // * DEC *
                // *******

                // Decrement memory by one:
                temp = (this.load(addr)-1)&0xFF;
                this.F_SIGN = (temp>>7)&1;
                this.F_ZERO = temp;
                this.write(addr, temp);
                break;

            }case 21:{

                // *******
                // * DEX *
                // *******

                // Decrement index X by one:
                this.REG_X = (this.REG_X-1)&0xFF;
                this.F_SIGN = (this.REG_X>>7)&1;
                this.F_ZERO = this.REG_X;
                break;

            }case 22:{

                // *******
                // * DEY *
                // *******

                // Decrement index Y by one:
                this.REG_Y = (this.REG_Y-1)&0xFF;
                this.F_SIGN = (this.REG_Y>>7)&1;
                this.F_ZERO = this.REG_Y;
                break;

            }case 23:{

                // *******
                // * EOR *
                // *******

                // XOR Memory with accumulator, store in accumulator:
                this.REG_ACC = (this.load(addr)^this.REG_ACC)&0xFF;
                this.F_SIGN = (this.REG_ACC>>7)&1;
                this.F_ZERO = this.REG_ACC;
                cycleCount+=cycleAdd;
                break;

            }case 24:{

                // *******
                // * INC *
                // *******

                // Increment memory by one:
                temp = (this.load(addr)+1)&0xFF;
                this.F_SIGN = (temp>>7)&1;
                this.F_ZERO = temp;
                this.write(addr, temp&0xFF);
                break;

            }case 25:{

                // *******
                // * INX *
                // *******

                // Increment index X by one:
                this.REG_X = (this.REG_X+1)&0xFF;
                this.F_SIGN = (this.REG_X>>7)&1;
                this.F_ZERO = this.REG_X;
                break;

            }case 26:{

                // *******
                // * INY *
                // *******

                // Increment index Y by one:
                this.REG_Y++;
                this.REG_Y &= 0xFF;
                this.F_SIGN = (this.REG_Y>>7)&1;
                this.F_ZERO = this.REG_Y;
                break;

            }case 27:{

                // *******
                // * JMP *
                // *******

                // Jump to new location:
                this.REG_PC = addr-1;
                break;

            }case 28:{

                // *******
                // * JSR *
                // *******

                // Jump to new location, saving return address.
                // Push return address on stack:
                this.push((this.REG_PC>>8)&255);
                this.push(this.REG_PC&255);
                this.REG_PC = addr-1;
                break;

            }case 29:{

                // *******
                // * LDA *
                // *******

                // Load accumulator with memory:
                this.REG_ACC = this.load(addr);
                this.F_SIGN = (this.REG_ACC>>7)&1;
                this.F_ZERO = this.REG_ACC;
                cycleCount+=cycleAdd;
                break;

            }case 30:{

                // *******
                // * LDX *
                // *******

                // Load index X with memory:
                this.REG_X = this.load(addr);
                this.F_SIGN = (this.REG_X>>7)&1;
                this.F_ZERO = this.REG_X;
                cycleCount+=cycleAdd;
                break;

            }case 31:{

                // *******
                // * LDY *
                // *******

                // Load index Y with memory:
                this.REG_Y = this.load(addr);
                this.F_SIGN = (this.REG_Y>>7)&1;
                this.F_ZERO = this.REG_Y;
                cycleCount+=cycleAdd;
                break;

            }case 32:{

                // *******
                // * LSR *
                // *******

                // Shift right one bit:
                if(addrMode == 4){ // ADDR_ACC

                    temp = (this.REG_ACC & 0xFF);
                    this.F_CARRY = temp&1;
                    temp >>= 1;
                    this.REG_ACC = temp;

                }else{

                    temp = this.load(addr) & 0xFF;
                    this.F_CARRY = temp&1;
                    temp >>= 1;
                    this.write(addr, temp);

                }
                this.F_SIGN = 0;
                this.F_ZERO = temp;
                break;

            }case 33:{

                // *******
                // * NOP *
                // *******

                // No OPeration.
                // Ignore.
                break;

            }case 34:{

                // *******
                // * ORA *
                // *******

                // OR memory with accumulator, store in accumulator.
                temp = (this.load(addr)|this.REG_ACC)&255;
                this.F_SIGN = (temp>>7)&1;
                this.F_ZERO = temp;
                this.REG_ACC = temp;
                if(addrMode!=11)cycleCount+=cycleAdd; // PostIdxInd = 11
                break;

            }case 35:{

                // *******
                // * PHA *
                // *******

                // Push accumulator on stack
                this.push(this.REG_ACC);
                break;

            }case 36:{

                // *******
                // * PHP *
                // *******

                // Push processor status on stack
                this.F_BRK = 1;
                this.push(
                    (this.F_CARRY)|
                    ((this.F_ZERO==0?1:0)<<1)|
                    (this.F_INTERRUPT<<2)|
                    (this.F_DECIMAL<<3)|
                    (this.F_BRK<<4)|
                    (this.F_NOTUSED<<5)|
                    (this.F_OVERFLOW<<6)|
                    (this.F_SIGN<<7)
                );
                break;

            }case 37:{

                // *******
                // * PLA *
                // *******

                // Pull accumulator from stack
                this.REG_ACC = this.pull();
                this.F_SIGN = (this.REG_ACC>>7)&1;
                this.F_ZERO = this.REG_ACC;
                break;

            }case 38:{

                // *******
                // * PLP *
                // *******

                // Pull processor status from stack
                temp = this.pull();
                this.F_CARRY     = (temp   )&1;
                this.F_ZERO      = (((temp>>1)&1)==1)?0:1;
                this.F_INTERRUPT = (temp>>2)&1;
                this.F_DECIMAL   = (temp>>3)&1;
                this.F_BRK       = (temp>>4)&1;
                this.F_NOTUSED   = (temp>>5)&1;
                this.F_OVERFLOW  = (temp>>6)&1;
                this.F_SIGN      = (temp>>7)&1;

                this.F_NOTUSED = 1;
                break;

            }case 39:{

                // *******
                // * ROL *
                // *******

                // Rotate one bit left
                if(addrMode == 4){ // ADDR_ACC = 4

                    temp = this.REG_ACC;
                    add = this.F_CARRY;
                    this.F_CARRY = (temp>>7)&1;
                    temp = ((temp<<1)&0xFF)+add;
                    this.REG_ACC = temp;

                }else{

                    temp = this.load(addr);
                    add = this.F_CARRY;
                    this.F_CARRY = (temp>>7)&1;
                    temp = ((temp<<1)&0xFF)+add;    
                    this.write(addr, temp);

                }
                this.F_SIGN = (temp>>7)&1;
                this.F_ZERO = temp;
                break;

            }case 40:{

                // *******
                // * ROR *
                // *******

                // Rotate one bit right
                if(addrMode == 4){ // ADDR_ACC = 4

                    add = this.F_CARRY<<7;
                    this.F_CARRY = this.REG_ACC&1;
                    temp = (this.REG_ACC>>1)+add;   
                    this.REG_ACC = temp;

                }else{

                    temp = this.load(addr);
                    add = this.F_CARRY<<7;
                    this.F_CARRY = temp&1;
                    temp = (temp>>1)+add;
                    this.write(addr, temp);

                }
                this.F_SIGN = (temp>>7)&1;
                this.F_ZERO = temp;
                break;

            }case 41:{

                // *******
                // * RTI *
                // *******

                // Return from interrupt. Pull status and PC from stack.
                
                temp = this.pull();
                this.F_CARRY     = (temp   )&1;
                this.F_ZERO      = ((temp>>1)&1)==0?1:0;
                this.F_INTERRUPT = (temp>>2)&1;
                this.F_DECIMAL   = (temp>>3)&1;
                this.F_BRK       = (temp>>4)&1;
                this.F_NOTUSED   = (temp>>5)&1;
                this.F_OVERFLOW  = (temp>>6)&1;
                this.F_SIGN      = (temp>>7)&1;

                this.REG_PC = this.pull();
                this.REG_PC += (this.pull()<<8);
                if(this.REG_PC==0xFFFF){
                    return;
                }
                this.REG_PC--;
                this.F_NOTUSED = 1;
                break;

            }case 42:{

                // *******
                // * RTS *
                // *******

                // Return from subroutine. Pull PC from stack.
                
                this.REG_PC = this.pull();
                this.REG_PC += (this.pull()<<8);
                
                if(this.REG_PC==0xFFFF){
                    return; // return from NSF play routine:
                }
                break;

            }case 43:{

                // *******
                // * SBC *
                // *******

                temp = this.REG_ACC-this.load(addr)-(1-this.F_CARRY);
                this.F_SIGN = (temp>>7)&1;
                this.F_ZERO = temp&0xFF;
                this.F_OVERFLOW = ((((this.REG_ACC^temp)&0x80)!=0 && ((this.REG_ACC^this.load(addr))&0x80)!=0)?1:0);
                this.F_CARRY = (temp<0?0:1);
                this.REG_ACC = (temp&0xFF);
                if(addrMode!=11)cycleCount+=cycleAdd; // PostIdxInd = 11
                break;

            }case 44:{

                // *******
                // * SEC *
                // *******

                // Set carry flag
                this.F_CARRY = 1;
                break;

            }case 45:{

                // *******
                // * SED *
                // *******

                // Set decimal mode
                this.F_DECIMAL = 1;
                break;

            }case 46:{

                // *******
                // * SEI *
                // *******

                // Set interrupt disable status
                this.F_INTERRUPT = 1;
                break;

            }case 47:{

                // *******
                // * STA *
                // *******

                // Store accumulator in memory
                this.write(addr, this.REG_ACC);
                break;

            }case 48:{

                // *******
                // * STX *
                // *******

                // Store index X in memory
                this.write(addr, this.REG_X);
                break;

            }case 49:{

                // *******
                // * STY *
                // *******

                // Store index Y in memory:
                this.write(addr, this.REG_Y);
                break;

            }case 50:{

                // *******
                // * TAX *
                // *******

                // Transfer accumulator to index X:
                this.REG_X = this.REG_ACC;
                this.F_SIGN = (this.REG_ACC>>7)&1;
                this.F_ZERO = this.REG_ACC;
                break;

            }case 51:{

                // *******
                // * TAY *
                // *******

                // Transfer accumulator to index Y:
                this.REG_Y = this.REG_ACC;
                this.F_SIGN = (this.REG_ACC>>7)&1;
                this.F_ZERO = this.REG_ACC;
                break;

            }case 52:{

                // *******
                // * TSX *
                // *******

                // Transfer stack pointer to index X:
                this.REG_X = (this.REG_SP-0x0100);
                this.F_SIGN = (this.REG_SP>>7)&1;
                this.F_ZERO = this.REG_X;
                break;

            }case 53:{

                // *******
                // * TXA *
                // *******

                // Transfer index X to accumulator:
                this.REG_ACC = this.REG_X;
                this.F_SIGN = (this.REG_X>>7)&1;
                this.F_ZERO = this.REG_X;
                break;

            }case 54:{

                // *******
                // * TXS *
                // *******

                // Transfer index X to stack pointer:
                this.REG_SP = (this.REG_X+0x0100);
                this.stackWrap();
                break;

            }case 55:{

                // *******
                // * TYA *
                // *******

                // Transfer index Y to accumulator:
                this.REG_ACC = this.REG_Y;
                this.F_SIGN = (this.REG_Y>>7)&1;
                this.F_ZERO = this.REG_Y;
                break;

            }default:{

                // *******
                // * ??? *
                // *******

                this.nes.stop();
                this.nes.crashMessage = "Game crashed, invalid opcode at address $"+opaddr.toString(16);
                break;

            }

        }// end of switch

        return cycleCount;

    },
    
    load: function(addr){
        if (addr < 0x2000) {
            return this.mem[addr & 0x7FF];
        }
        else {
            return this.nes.mmap.load(addr);
        }
    },
    
    load16bit: function(addr){
        if (addr < 0x1FFF) {
            return this.mem[addr&0x7FF] 
                | (this.mem[(addr+1)&0x7FF]<<8);
        }
        else {
            return this.nes.mmap.load(addr) | (this.nes.mmap.load(addr+1) << 8);
        }
    },
    
    write: function(addr, val){
        if(addr < 0x2000) {
            this.mem[addr&0x7FF] = val;
        }
        else {
            this.nes.mmap.write(addr,val);
        }
    },

    requestIrq: function(type){
        if(this.irqRequested){
            if(type == this.IRQ_NORMAL){
                return;
            }
            ////System.out.println("too fast irqs. type="+type);
        }
        this.irqRequested = true;
        this.irqType = type;
    },

    push: function(value){
        this.nes.mmap.write(this.REG_SP, value);
        this.REG_SP--;
        this.REG_SP = 0x0100 | (this.REG_SP&0xFF);
    },

    stackWrap: function(){
        this.REG_SP = 0x0100 | (this.REG_SP&0xFF);
    },

    pull: function(){
        this.REG_SP++;
        this.REG_SP = 0x0100 | (this.REG_SP&0xFF);
        return this.nes.mmap.load(this.REG_SP);
    },

    pageCrossed: function(addr1, addr2){
        return ((addr1&0xFF00) != (addr2&0xFF00));
    },

    haltCycles: function(cycles){
        this.cyclesToHalt += cycles;
    },

    doNonMaskableInterrupt: function(status){
        if((this.nes.mmap.load(0x2000) & 128) != 0) { // Check whether VBlank Interrupts are enabled

            this.REG_PC_NEW++;
            this.push((this.REG_PC_NEW>>8)&0xFF);
            this.push(this.REG_PC_NEW&0xFF);
            //this.F_INTERRUPT_NEW = 1;
            this.push(status);

            this.REG_PC_NEW = this.nes.mmap.load(0xFFFA) | (this.nes.mmap.load(0xFFFB) << 8);
            this.REG_PC_NEW--;
        }
    },

    doResetInterrupt: function(){
        this.REG_PC_NEW = this.nes.mmap.load(0xFFFC) | (this.nes.mmap.load(0xFFFD) << 8);
        this.REG_PC_NEW--;
    },

    doIrq: function(status){
        this.REG_PC_NEW++;
        this.push((this.REG_PC_NEW>>8)&0xFF);
        this.push(this.REG_PC_NEW&0xFF);
        this.push(status);
        this.F_INTERRUPT_NEW = 1;
        this.F_BRK_NEW = 0;

        this.REG_PC_NEW = this.nes.mmap.load(0xFFFE) | (this.nes.mmap.load(0xFFFF) << 8);
        this.REG_PC_NEW--;
    },

    getStatus: function(){
        return (this.F_CARRY)
                |(this.F_ZERO<<1)
                |(this.F_INTERRUPT<<2)
                |(this.F_DECIMAL<<3)
                |(this.F_BRK<<4)
                |(this.F_NOTUSED<<5)
                |(this.F_OVERFLOW<<6)
                |(this.F_SIGN<<7);
    },

    setStatus: function(st){
        this.F_CARRY     = (st   )&1;
        this.F_ZERO      = (st>>1)&1;
        this.F_INTERRUPT = (st>>2)&1;
        this.F_DECIMAL   = (st>>3)&1;
        this.F_BRK       = (st>>4)&1;
        this.F_NOTUSED   = (st>>5)&1;
        this.F_OVERFLOW  = (st>>6)&1;
        this.F_SIGN      = (st>>7)&1;
    },
    
    JSON_PROPERTIES: [
        'mem', 'cyclesToHalt', 'irqRequested', 'irqType',
        // Registers
        'REG_ACC', 'REG_X', 'REG_Y', 'REG_SP', 'REG_PC', 'REG_PC_NEW',
        'REG_STATUS',
        // Status
        'F_CARRY', 'F_DECIMAL', 'F_INTERRUPT', 'F_INTERRUPT_NEW', 'F_OVERFLOW', 
        'F_SIGN', 'F_ZERO', 'F_NOTUSED', 'F_NOTUSED_NEW', 'F_BRK', 'F_BRK_NEW'
    ],
    
    toJSON: function() {
        return JSNES.Utils.toJSON(this);
    },
    
    fromJSON: function(s) {
        JSNES.Utils.fromJSON(this, s);
    }
}

// Generates and provides an array of details about instructions
JSNES.CPU.OpData = function() {
    this.opdata = new Array(256);
    
    // Set all to invalid instruction (to detect crashes):
    for(var i=0;i<256;i++) this.opdata[i]=0xFF;
    
    // Now fill in all valid opcodes:
    
    // ADC:
    this.setOp(this.INS_ADC,0x69,this.ADDR_IMM,2,2);
    this.setOp(this.INS_ADC,0x65,this.ADDR_ZP,2,3);
    this.setOp(this.INS_ADC,0x75,this.ADDR_ZPX,2,4);
    this.setOp(this.INS_ADC,0x6D,this.ADDR_ABS,3,4);
    this.setOp(this.INS_ADC,0x7D,this.ADDR_ABSX,3,4);
    this.setOp(this.INS_ADC,0x79,this.ADDR_ABSY,3,4);
    this.setOp(this.INS_ADC,0x61,this.ADDR_PREIDXIND,2,6);
    this.setOp(this.INS_ADC,0x71,this.ADDR_POSTIDXIND,2,5);
    
    // AND:
    this.setOp(this.INS_AND,0x29,this.ADDR_IMM,2,2);
    this.setOp(this.INS_AND,0x25,this.ADDR_ZP,2,3);
    this.setOp(this.INS_AND,0x35,this.ADDR_ZPX,2,4);
    this.setOp(this.INS_AND,0x2D,this.ADDR_ABS,3,4);
    this.setOp(this.INS_AND,0x3D,this.ADDR_ABSX,3,4);
    this.setOp(this.INS_AND,0x39,this.ADDR_ABSY,3,4);
    this.setOp(this.INS_AND,0x21,this.ADDR_PREIDXIND,2,6);
    this.setOp(this.INS_AND,0x31,this.ADDR_POSTIDXIND,2,5);
    
    // ASL:
    this.setOp(this.INS_ASL,0x0A,this.ADDR_ACC,1,2);
    this.setOp(this.INS_ASL,0x06,this.ADDR_ZP,2,5);
    this.setOp(this.INS_ASL,0x16,this.ADDR_ZPX,2,6);
    this.setOp(this.INS_ASL,0x0E,this.ADDR_ABS,3,6);
    this.setOp(this.INS_ASL,0x1E,this.ADDR_ABSX,3,7);
    
    // BCC:
    this.setOp(this.INS_BCC,0x90,this.ADDR_REL,2,2);
    
    // BCS:
    this.setOp(this.INS_BCS,0xB0,this.ADDR_REL,2,2);
    
    // BEQ:
    this.setOp(this.INS_BEQ,0xF0,this.ADDR_REL,2,2);
    
    // BIT:
    this.setOp(this.INS_BIT,0x24,this.ADDR_ZP,2,3);
    this.setOp(this.INS_BIT,0x2C,this.ADDR_ABS,3,4);
    
    // BMI:
    this.setOp(this.INS_BMI,0x30,this.ADDR_REL,2,2);
    
    // BNE:
    this.setOp(this.INS_BNE,0xD0,this.ADDR_REL,2,2);
    
    // BPL:
    this.setOp(this.INS_BPL,0x10,this.ADDR_REL,2,2);
    
    // BRK:
    this.setOp(this.INS_BRK,0x00,this.ADDR_IMP,1,7);
    
    // BVC:
    this.setOp(this.INS_BVC,0x50,this.ADDR_REL,2,2);
    
    // BVS:
    this.setOp(this.INS_BVS,0x70,this.ADDR_REL,2,2);
    
    // CLC:
    this.setOp(this.INS_CLC,0x18,this.ADDR_IMP,1,2);
    
    // CLD:
    this.setOp(this.INS_CLD,0xD8,this.ADDR_IMP,1,2);
    
    // CLI:
    this.setOp(this.INS_CLI,0x58,this.ADDR_IMP,1,2);
    
    // CLV:
    this.setOp(this.INS_CLV,0xB8,this.ADDR_IMP,1,2);
    
    // CMP:
    this.setOp(this.INS_CMP,0xC9,this.ADDR_IMM,2,2);
    this.setOp(this.INS_CMP,0xC5,this.ADDR_ZP,2,3);
    this.setOp(this.INS_CMP,0xD5,this.ADDR_ZPX,2,4);
    this.setOp(this.INS_CMP,0xCD,this.ADDR_ABS,3,4);
    this.setOp(this.INS_CMP,0xDD,this.ADDR_ABSX,3,4);
    this.setOp(this.INS_CMP,0xD9,this.ADDR_ABSY,3,4);
    this.setOp(this.INS_CMP,0xC1,this.ADDR_PREIDXIND,2,6);
    this.setOp(this.INS_CMP,0xD1,this.ADDR_POSTIDXIND,2,5);
    
    // CPX:
    this.setOp(this.INS_CPX,0xE0,this.ADDR_IMM,2,2);
    this.setOp(this.INS_CPX,0xE4,this.ADDR_ZP,2,3);
    this.setOp(this.INS_CPX,0xEC,this.ADDR_ABS,3,4);
    
    // CPY:
    this.setOp(this.INS_CPY,0xC0,this.ADDR_IMM,2,2);
    this.setOp(this.INS_CPY,0xC4,this.ADDR_ZP,2,3);
    this.setOp(this.INS_CPY,0xCC,this.ADDR_ABS,3,4);
    
    // DEC:
    this.setOp(this.INS_DEC,0xC6,this.ADDR_ZP,2,5);
    this.setOp(this.INS_DEC,0xD6,this.ADDR_ZPX,2,6);
    this.setOp(this.INS_DEC,0xCE,this.ADDR_ABS,3,6);
    this.setOp(this.INS_DEC,0xDE,this.ADDR_ABSX,3,7);
    
    // DEX:
    this.setOp(this.INS_DEX,0xCA,this.ADDR_IMP,1,2);
    
    // DEY:
    this.setOp(this.INS_DEY,0x88,this.ADDR_IMP,1,2);
    
    // EOR:
    this.setOp(this.INS_EOR,0x49,this.ADDR_IMM,2,2);
    this.setOp(this.INS_EOR,0x45,this.ADDR_ZP,2,3);
    this.setOp(this.INS_EOR,0x55,this.ADDR_ZPX,2,4);
    this.setOp(this.INS_EOR,0x4D,this.ADDR_ABS,3,4);
    this.setOp(this.INS_EOR,0x5D,this.ADDR_ABSX,3,4);
    this.setOp(this.INS_EOR,0x59,this.ADDR_ABSY,3,4);
    this.setOp(this.INS_EOR,0x41,this.ADDR_PREIDXIND,2,6);
    this.setOp(this.INS_EOR,0x51,this.ADDR_POSTIDXIND,2,5);
    
    // INC:
    this.setOp(this.INS_INC,0xE6,this.ADDR_ZP,2,5);
    this.setOp(this.INS_INC,0xF6,this.ADDR_ZPX,2,6);
    this.setOp(this.INS_INC,0xEE,this.ADDR_ABS,3,6);
    this.setOp(this.INS_INC,0xFE,this.ADDR_ABSX,3,7);
    
    // INX:
    this.setOp(this.INS_INX,0xE8,this.ADDR_IMP,1,2);
    
    // INY:
    this.setOp(this.INS_INY,0xC8,this.ADDR_IMP,1,2);
    
    // JMP:
    this.setOp(this.INS_JMP,0x4C,this.ADDR_ABS,3,3);
    this.setOp(this.INS_JMP,0x6C,this.ADDR_INDABS,3,5);
    
    // JSR:
    this.setOp(this.INS_JSR,0x20,this.ADDR_ABS,3,6);
    
    // LDA:
    this.setOp(this.INS_LDA,0xA9,this.ADDR_IMM,2,2);
    this.setOp(this.INS_LDA,0xA5,this.ADDR_ZP,2,3);
    this.setOp(this.INS_LDA,0xB5,this.ADDR_ZPX,2,4);
    this.setOp(this.INS_LDA,0xAD,this.ADDR_ABS,3,4);
    this.setOp(this.INS_LDA,0xBD,this.ADDR_ABSX,3,4);
    this.setOp(this.INS_LDA,0xB9,this.ADDR_ABSY,3,4);
    this.setOp(this.INS_LDA,0xA1,this.ADDR_PREIDXIND,2,6);
    this.setOp(this.INS_LDA,0xB1,this.ADDR_POSTIDXIND,2,5);
    
    
    // LDX:
    this.setOp(this.INS_LDX,0xA2,this.ADDR_IMM,2,2);
    this.setOp(this.INS_LDX,0xA6,this.ADDR_ZP,2,3);
    this.setOp(this.INS_LDX,0xB6,this.ADDR_ZPY,2,4);
    this.setOp(this.INS_LDX,0xAE,this.ADDR_ABS,3,4);
    this.setOp(this.INS_LDX,0xBE,this.ADDR_ABSY,3,4);
    
    // LDY:
    this.setOp(this.INS_LDY,0xA0,this.ADDR_IMM,2,2);
    this.setOp(this.INS_LDY,0xA4,this.ADDR_ZP,2,3);
    this.setOp(this.INS_LDY,0xB4,this.ADDR_ZPX,2,4);
    this.setOp(this.INS_LDY,0xAC,this.ADDR_ABS,3,4);
    this.setOp(this.INS_LDY,0xBC,this.ADDR_ABSX,3,4);
    
    // LSR:
    this.setOp(this.INS_LSR,0x4A,this.ADDR_ACC,1,2);
    this.setOp(this.INS_LSR,0x46,this.ADDR_ZP,2,5);
    this.setOp(this.INS_LSR,0x56,this.ADDR_ZPX,2,6);
    this.setOp(this.INS_LSR,0x4E,this.ADDR_ABS,3,6);
    this.setOp(this.INS_LSR,0x5E,this.ADDR_ABSX,3,7);
    
    // NOP:
    this.setOp(this.INS_NOP,0xEA,this.ADDR_IMP,1,2);
    
    // ORA:
    this.setOp(this.INS_ORA,0x09,this.ADDR_IMM,2,2);
    this.setOp(this.INS_ORA,0x05,this.ADDR_ZP,2,3);
    this.setOp(this.INS_ORA,0x15,this.ADDR_ZPX,2,4);
    this.setOp(this.INS_ORA,0x0D,this.ADDR_ABS,3,4);
    this.setOp(this.INS_ORA,0x1D,this.ADDR_ABSX,3,4);
    this.setOp(this.INS_ORA,0x19,this.ADDR_ABSY,3,4);
    this.setOp(this.INS_ORA,0x01,this.ADDR_PREIDXIND,2,6);
    this.setOp(this.INS_ORA,0x11,this.ADDR_POSTIDXIND,2,5);
    
    // PHA:
    this.setOp(this.INS_PHA,0x48,this.ADDR_IMP,1,3);
    
    // PHP:
    this.setOp(this.INS_PHP,0x08,this.ADDR_IMP,1,3);
    
    // PLA:
    this.setOp(this.INS_PLA,0x68,this.ADDR_IMP,1,4);
    
    // PLP:
    this.setOp(this.INS_PLP,0x28,this.ADDR_IMP,1,4);
    
    // ROL:
    this.setOp(this.INS_ROL,0x2A,this.ADDR_ACC,1,2);
    this.setOp(this.INS_ROL,0x26,this.ADDR_ZP,2,5);
    this.setOp(this.INS_ROL,0x36,this.ADDR_ZPX,2,6);
    this.setOp(this.INS_ROL,0x2E,this.ADDR_ABS,3,6);
    this.setOp(this.INS_ROL,0x3E,this.ADDR_ABSX,3,7);
    
    // ROR:
    this.setOp(this.INS_ROR,0x6A,this.ADDR_ACC,1,2);
    this.setOp(this.INS_ROR,0x66,this.ADDR_ZP,2,5);
    this.setOp(this.INS_ROR,0x76,this.ADDR_ZPX,2,6);
    this.setOp(this.INS_ROR,0x6E,this.ADDR_ABS,3,6);
    this.setOp(this.INS_ROR,0x7E,this.ADDR_ABSX,3,7);
    
    // RTI:
    this.setOp(this.INS_RTI,0x40,this.ADDR_IMP,1,6);
    
    // RTS:
    this.setOp(this.INS_RTS,0x60,this.ADDR_IMP,1,6);
    
    // SBC:
    this.setOp(this.INS_SBC,0xE9,this.ADDR_IMM,2,2);
    this.setOp(this.INS_SBC,0xE5,this.ADDR_ZP,2,3);
    this.setOp(this.INS_SBC,0xF5,this.ADDR_ZPX,2,4);
    this.setOp(this.INS_SBC,0xED,this.ADDR_ABS,3,4);
    this.setOp(this.INS_SBC,0xFD,this.ADDR_ABSX,3,4);
    this.setOp(this.INS_SBC,0xF9,this.ADDR_ABSY,3,4);
    this.setOp(this.INS_SBC,0xE1,this.ADDR_PREIDXIND,2,6);
    this.setOp(this.INS_SBC,0xF1,this.ADDR_POSTIDXIND,2,5);
    
    // SEC:
    this.setOp(this.INS_SEC,0x38,this.ADDR_IMP,1,2);
    
    // SED:
    this.setOp(this.INS_SED,0xF8,this.ADDR_IMP,1,2);
    
    // SEI:
    this.setOp(this.INS_SEI,0x78,this.ADDR_IMP,1,2);
    
    // STA:
    this.setOp(this.INS_STA,0x85,this.ADDR_ZP,2,3);
    this.setOp(this.INS_STA,0x95,this.ADDR_ZPX,2,4);
    this.setOp(this.INS_STA,0x8D,this.ADDR_ABS,3,4);
    this.setOp(this.INS_STA,0x9D,this.ADDR_ABSX,3,5);
    this.setOp(this.INS_STA,0x99,this.ADDR_ABSY,3,5);
    this.setOp(this.INS_STA,0x81,this.ADDR_PREIDXIND,2,6);
    this.setOp(this.INS_STA,0x91,this.ADDR_POSTIDXIND,2,6);
    
    // STX:
    this.setOp(this.INS_STX,0x86,this.ADDR_ZP,2,3);
    this.setOp(this.INS_STX,0x96,this.ADDR_ZPY,2,4);
    this.setOp(this.INS_STX,0x8E,this.ADDR_ABS,3,4);
    
    // STY:
    this.setOp(this.INS_STY,0x84,this.ADDR_ZP,2,3);
    this.setOp(this.INS_STY,0x94,this.ADDR_ZPX,2,4);
    this.setOp(this.INS_STY,0x8C,this.ADDR_ABS,3,4);
    
    // TAX:
    this.setOp(this.INS_TAX,0xAA,this.ADDR_IMP,1,2);
    
    // TAY:
    this.setOp(this.INS_TAY,0xA8,this.ADDR_IMP,1,2);
    
    // TSX:
    this.setOp(this.INS_TSX,0xBA,this.ADDR_IMP,1,2);
    
    // TXA:
    this.setOp(this.INS_TXA,0x8A,this.ADDR_IMP,1,2);
    
    // TXS:
    this.setOp(this.INS_TXS,0x9A,this.ADDR_IMP,1,2);
    
    // TYA:
    this.setOp(this.INS_TYA,0x98,this.ADDR_IMP,1,2);
    
    this.cycTable = new Array(
    /*0x00*/ 7,6,2,8,3,3,5,5,3,2,2,2,4,4,6,6,
    /*0x10*/ 2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,
    /*0x20*/ 6,6,2,8,3,3,5,5,4,2,2,2,4,4,6,6,
    /*0x30*/ 2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,
    /*0x40*/ 6,6,2,8,3,3,5,5,3,2,2,2,3,4,6,6,
    /*0x50*/ 2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,
    /*0x60*/ 6,6,2,8,3,3,5,5,4,2,2,2,5,4,6,6,
    /*0x70*/ 2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,
    /*0x80*/ 2,6,2,6,3,3,3,3,2,2,2,2,4,4,4,4,
    /*0x90*/ 2,6,2,6,4,4,4,4,2,5,2,5,5,5,5,5,
    /*0xA0*/ 2,6,2,6,3,3,3,3,2,2,2,2,4,4,4,4,
    /*0xB0*/ 2,5,2,5,4,4,4,4,2,4,2,4,4,4,4,4,
    /*0xC0*/ 2,6,2,8,3,3,5,5,2,2,2,2,4,4,6,6,
    /*0xD0*/ 2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7,
    /*0xE0*/ 2,6,3,8,3,3,5,5,2,2,2,2,4,4,6,6,
    /*0xF0*/ 2,5,2,8,4,4,6,6,2,4,2,7,4,4,7,7
    );
    
    
    this.instname = new Array(56);
    
    // Instruction Names:
    this.instname[ 0] = "ADC";
    this.instname[ 1] = "AND";
    this.instname[ 2] = "ASL";
    this.instname[ 3] = "BCC";
    this.instname[ 4] = "BCS";
    this.instname[ 5] = "BEQ";
    this.instname[ 6] = "BIT";
    this.instname[ 7] = "BMI";
    this.instname[ 8] = "BNE";
    this.instname[ 9] = "BPL";
    this.instname[10] = "BRK";
    this.instname[11] = "BVC";
    this.instname[12] = "BVS";
    this.instname[13] = "CLC";
    this.instname[14] = "CLD";
    this.instname[15] = "CLI";
    this.instname[16] = "CLV";
    this.instname[17] = "CMP";
    this.instname[18] = "CPX";
    this.instname[19] = "CPY";
    this.instname[20] = "DEC";
    this.instname[21] = "DEX";
    this.instname[22] = "DEY";
    this.instname[23] = "EOR";
    this.instname[24] = "INC";
    this.instname[25] = "INX";
    this.instname[26] = "INY";
    this.instname[27] = "JMP";
    this.instname[28] = "JSR";
    this.instname[29] = "LDA";
    this.instname[30] = "LDX";
    this.instname[31] = "LDY";
    this.instname[32] = "LSR";
    this.instname[33] = "NOP";
    this.instname[34] = "ORA";
    this.instname[35] = "PHA";
    this.instname[36] = "PHP";
    this.instname[37] = "PLA";
    this.instname[38] = "PLP";
    this.instname[39] = "ROL";
    this.instname[40] = "ROR";
    this.instname[41] = "RTI";
    this.instname[42] = "RTS";
    this.instname[43] = "SBC";
    this.instname[44] = "SEC";
    this.instname[45] = "SED";
    this.instname[46] = "SEI";
    this.instname[47] = "STA";
    this.instname[48] = "STX";
    this.instname[49] = "STY";
    this.instname[50] = "TAX";
    this.instname[51] = "TAY";
    this.instname[52] = "TSX";
    this.instname[53] = "TXA";
    this.instname[54] = "TXS";
    this.instname[55] = "TYA";
    
    this.addrDesc = new Array(
        "Zero Page           ",
        "Relative            ",
        "Implied             ",
        "Absolute            ",
        "Accumulator         ",
        "Immediate           ",
        "Zero Page,X         ",
        "Zero Page,Y         ",
        "Absolute,X          ",
        "Absolute,Y          ",
        "Preindexed Indirect ",
        "Postindexed Indirect",
        "Indirect Absolute   "
    );
}

JSNES.CPU.OpData.prototype = {
    INS_ADC: 0,
    INS_AND: 1,
    INS_ASL: 2,
    
    INS_BCC: 3,
    INS_BCS: 4,
    INS_BEQ: 5,
    INS_BIT: 6,
    INS_BMI: 7,
    INS_BNE: 8,
    INS_BPL: 9,
    INS_BRK: 10,
    INS_BVC: 11,
    INS_BVS: 12,
    
    INS_CLC: 13,
    INS_CLD: 14,
    INS_CLI: 15,
    INS_CLV: 16,
    INS_CMP: 17,
    INS_CPX: 18,
    INS_CPY: 19,
    
    INS_DEC: 20,
    INS_DEX: 21,
    INS_DEY: 22,
    
    INS_EOR: 23,
    
    INS_INC: 24,
    INS_INX: 25,
    INS_INY: 26,
    
    INS_JMP: 27,
    INS_JSR: 28,
    
    INS_LDA: 29,
    INS_LDX: 30,
    INS_LDY: 31,
    INS_LSR: 32,
    
    INS_NOP: 33,
    
    INS_ORA: 34,
    
    INS_PHA: 35,
    INS_PHP: 36,
    INS_PLA: 37,
    INS_PLP: 38,
    
    INS_ROL: 39,
    INS_ROR: 40,
    INS_RTI: 41,
    INS_RTS: 42,
    
    INS_SBC: 43,
    INS_SEC: 44,
    INS_SED: 45,
    INS_SEI: 46,
    INS_STA: 47,
    INS_STX: 48,
    INS_STY: 49,
    
    INS_TAX: 50,
    INS_TAY: 51,
    INS_TSX: 52,
    INS_TXA: 53,
    INS_TXS: 54,
    INS_TYA: 55,
    
    INS_DUMMY: 56, // dummy instruction used for 'halting' the processor some cycles
    
    // -------------------------------- //
    
    // Addressing modes:
    ADDR_ZP        : 0,
    ADDR_REL       : 1,
    ADDR_IMP       : 2,
    ADDR_ABS       : 3,
    ADDR_ACC       : 4,
    ADDR_IMM       : 5,
    ADDR_ZPX       : 6,
    ADDR_ZPY       : 7,
    ADDR_ABSX      : 8,
    ADDR_ABSY      : 9,
    ADDR_PREIDXIND : 10,
    ADDR_POSTIDXIND: 11,
    ADDR_INDABS    : 12,
    
    setOp: function(inst, op, addr, size, cycles){
        this.opdata[op] = 
            ((inst  &0xFF)    )| 
            ((addr  &0xFF)<< 8)| 
            ((size  &0xFF)<<16)| 
            ((cycles&0xFF)<<24);
    }
};