Skip to content


Subversion checkout URL

You can clone with
Download ZIP
Tree: 841ee3454c
Fetching contributors…

Cannot retrieve contributors at this time

428 lines (404 sloc) 10.741 kB
package main
import (
var (
c *Cpu
pc uint16
func immediateAddress() int {
val, _ := Ram.Read(pc - 1)
return int(val)
func absoluteAddress() (result int) {
// Switch to an int (or more appropriately uint16) since we
// will overflow when shifting the high byte
high, _ := Ram.Read(pc + 1)
low, _ := Ram.Read(pc)
return (int(high) << 8) + int(low)
func zeroPageAddress() int {
res, _ := Ram.Read(pc)
return int(res)
func indirectAbsoluteAddress() (result int) {
high, _ := Ram.Read(pc + 1)
low, _ := Ram.Read(pc)
result = (int(high) << 8) + int(low)
func absoluteIndexedAddress(index Word) (result int) {
// Switch to an int (or more appropriately uint16) since we
// will overflow when shifting the high byte
high, _ := Ram.Read(pc + 1)
low, _ := Ram.Read(pc)
return (int(high) << 8) + int(low) + int(index)
func zeroPageIndexedAddress(index Word) int {
location, _ := Ram.Read(pc)
return int(location + index)
func indexedIndirectAddress() int {
location, _ := Ram.Read(pc)
location = location + c.X
// Switch to an int (or more appropriately uint16) since we
// will overflow when shifting the high byte
high, _ := Ram.Read(location + 1)
low, _ := Ram.Read(location)
return (int(high) << 8) + int(low)
func indirectIndexedAddress() int {
location, _ := Ram.Read(pc)
// Switch to an int (or more appropriately uint16) since we
// will overflow when shifting the high byte
high, _ := Ram.Read(location + 1)
low, _ := Ram.Read(location)
return (int(high) << 8) + int(low) + int(c.Y)
func relativeAddress() int {
return 0
func accumulatorAddress() int {
return 0
func Disassemble(opcode Word, cpu *Cpu, p uint16) {
c = cpu
pc = p
fmt.Printf("0x%X: 0x%X ", pc-1, opcode)
switch opcode {
// ADC
case 0x69:
fmt.Printf("ADC $%X\n", immediateAddress())
case 0x65:
fmt.Printf("ADC $%X\n", zeroPageAddress())
case 0x75:
fmt.Printf("ADC $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x6D:
fmt.Printf("ADC $%X\n", absoluteAddress())
case 0x7D:
fmt.Printf("ADC $%X,X\n", absoluteIndexedAddress(c.X))
case 0x79:
fmt.Printf("ADC $%X,Y\n", absoluteIndexedAddress(c.Y))
case 0x61:
fmt.Printf("ADC ($%X,X)\n", indexedIndirectAddress())
case 0x71:
fmt.Printf("ADC ($%X),Y\n", indirectIndexedAddress())
// LDA
case 0xA9:
fmt.Printf("LDA $%X\n", immediateAddress())
case 0xA5:
fmt.Printf("LDA $%X\n", zeroPageAddress())
case 0xB5:
fmt.Printf("LDA $%X,X\n", zeroPageIndexedAddress(c.X))
case 0xAD:
fmt.Printf("LDA $%X\n", absoluteAddress())
case 0xBD:
fmt.Printf("LDA $%X,X\n", absoluteIndexedAddress(c.X))
case 0xB9:
fmt.Printf("LDA $%X,Y\n", absoluteIndexedAddress(c.Y))
case 0xA1:
fmt.Printf("LDA ($%X,X)\n", indexedIndirectAddress())
case 0xB1:
fmt.Printf("LDA ($%X),Y\n", indirectIndexedAddress())
// LDX
case 0xA2:
fmt.Printf("LDX $%X\n", immediateAddress())
case 0xA6:
fmt.Printf("LDX $%X\n", zeroPageAddress())
case 0xB6:
fmt.Printf("LDX $%X,X\n", zeroPageIndexedAddress(c.X))
case 0xAE:
fmt.Printf("LDX $%X\n", absoluteAddress())
case 0xBE:
fmt.Printf("LDX $%X,Y\n", absoluteIndexedAddress(c.Y))
// LDY
case 0xA0:
fmt.Printf("LDY $%X\n", immediateAddress())
case 0xA4:
fmt.Printf("LDY $%X\n", zeroPageAddress())
case 0xB4:
fmt.Printf("LDY $%X,X\n", zeroPageIndexedAddress(c.X))
case 0xAC:
fmt.Printf("LDY $%X\n", absoluteAddress())
case 0xBC:
fmt.Printf("LDY $%X,X\n", absoluteIndexedAddress(c.X))
// STA
case 0x85:
fmt.Printf("STA $%X\n", zeroPageAddress())
case 0x95:
fmt.Printf("STA $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x8D:
fmt.Printf("STA $%X\n", absoluteAddress())
case 0x9D:
fmt.Printf("STA $%X,X\n", absoluteIndexedAddress(c.X))
case 0x99:
fmt.Printf("STA $%X,Y\n", absoluteIndexedAddress(c.Y))
case 0x81:
fmt.Printf("STA ($%X,X)\n", indexedIndirectAddress())
case 0x91:
fmt.Printf("STA ($%X),Y\n", indirectIndexedAddress())
// STX
case 0x86:
fmt.Printf("STX $%X\n", zeroPageAddress())
case 0x96:
fmt.Printf("STX $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x8E:
fmt.Printf("STX $%X\n", absoluteAddress())
// STY
case 0x84:
fmt.Printf("STY $%X\n", zeroPageAddress())
case 0x94:
fmt.Printf("STY $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x8C:
fmt.Printf("STY $%X\n", absoluteAddress())
// JMP
case 0x4C:
fmt.Printf("JMP $%X\n", absoluteAddress())
case 0x6C:
fmt.Printf("JMP $%X\n", indirectAbsoluteAddress())
// JSR
case 0x20:
fmt.Printf("JSR $%X\n", absoluteAddress())
// Register Instructions
case 0xAA:
case 0x8A:
case 0xCA:
case 0xE8:
case 0xA8:
case 0x98:
case 0x88:
case 0xC8:
// Branch Instructions
case 0x10:
fmt.Printf("BPL $%X\n", immediateAddress())
case 0x30:
fmt.Printf("BMI $%X\n", immediateAddress())
case 0x50:
fmt.Printf("BVC $%X\n", immediateAddress())
case 0x70:
fmt.Printf("BVS $%X\n", immediateAddress())
case 0x90:
fmt.Printf("BCC $%X\n", immediateAddress())
case 0xB0:
fmt.Printf("BCS $%X\n", immediateAddress())
case 0xD0:
fmt.Printf("BNE $%X\n", immediateAddress())
case 0xF0:
fmt.Printf("BEQ $%X\n", immediateAddress())
// CMP
case 0xC9:
fmt.Printf("CMP $%X\n", immediateAddress())
case 0xC5:
fmt.Printf("CMP $%X\n", zeroPageAddress())
case 0xD5:
fmt.Printf("CMP $%X,X\n", zeroPageIndexedAddress(c.X))
case 0xCD:
fmt.Printf("CMP $%X\n", absoluteAddress())
case 0xDD:
fmt.Printf("CMP $%X,X\n", absoluteIndexedAddress(c.X))
case 0xD9:
fmt.Printf("CMP $%X,Y\n", absoluteIndexedAddress(c.Y))
case 0xC1:
fmt.Printf("CMP ($%X,X)\n", indexedIndirectAddress())
case 0xD1:
fmt.Printf("CMP ($%X),Y\n", c.indirectIndexedAddress())
// CPX
case 0xE0:
fmt.Printf("CPX $%X\n", immediateAddress())
case 0xE4:
fmt.Printf("CPX $%X\n", zeroPageAddress())
case 0xEC:
fmt.Printf("CPX $%X\n", absoluteAddress())
// CPY
case 0xC0:
fmt.Printf("CPY $%X\n", immediateAddress())
case 0xC4:
fmt.Printf("CPY $%X\n", zeroPageAddress())
case 0xCC:
fmt.Printf("CPY $%X\n", absoluteAddress())
// SBC
case 0xE9:
fmt.Printf("SBC $%X\n", immediateAddress())
case 0xE5:
fmt.Printf("SBC $%X\n", zeroPageAddress())
case 0xF5:
fmt.Printf("SBC $%X,X\n", zeroPageIndexedAddress(c.X))
case 0xED:
fmt.Printf("SBC $%X\n", absoluteAddress())
case 0xFD:
fmt.Printf("SBC $%X,X\n", absoluteIndexedAddress(c.X))
case 0xF9:
fmt.Printf("SBC $%X,Y\n", absoluteIndexedAddress(c.Y))
case 0xE1:
fmt.Printf("SBC ($%X,X)\n", indexedIndirectAddress())
case 0xF1:
fmt.Printf("SBC ($%X),Y\n", indirectIndexedAddress())
// Flag Instructions
case 0x18:
case 0x38:
case 0x58:
case 0x78:
case 0xB8:
case 0xD8:
case 0xF8:
// Stack instructions
case 0x9A:
case 0xBA:
case 0x48:
case 0x68:
case 0x08:
case 0x28:
// AND
case 0x29:
fmt.Printf("AND $%X\n", immediateAddress())
case 0x25:
fmt.Printf("AND $%X\n", zeroPageAddress())
case 0x35:
fmt.Printf("AND $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x2d:
fmt.Printf("AND $%X\n", absoluteAddress())
case 0x3d:
fmt.Printf("AND $%X,X\n", absoluteIndexedAddress(c.X))
case 0x39:
fmt.Printf("AND $%X,Y\n", absoluteIndexedAddress(c.Y))
case 0x21:
fmt.Printf("AND ($%X,X)\n", indexedIndirectAddress())
case 0x31:
fmt.Printf("AND ($%X),Y\n", indirectIndexedAddress())
// ORA
case 0x09:
fmt.Printf("ORA $%X\n", immediateAddress())
case 0x05:
fmt.Printf("ORA $%X\n", zeroPageAddress())
case 0x15:
fmt.Printf("ORA $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x0d:
fmt.Printf("ORA $%X\n", absoluteAddress())
case 0x1d:
fmt.Printf("ORA $%X,X\n", absoluteIndexedAddress(c.X))
case 0x19:
fmt.Printf("ORA $%X,Y\n", absoluteIndexedAddress(c.Y))
case 0x01:
fmt.Printf("ORA ($%X,X)\n", indexedIndirectAddress())
case 0x11:
fmt.Printf("ORA ($%X),Y\n", indirectIndexedAddress())
// EOR
case 0x49:
fmt.Printf("EOR $%X\n", immediateAddress())
case 0x45:
fmt.Printf("EOR $%X\n", zeroPageAddress())
case 0x55:
fmt.Printf("EOR $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x4d:
fmt.Printf("EOR $%X\n", absoluteAddress())
case 0x5d:
fmt.Printf("EOR $%X,X\n", absoluteIndexedAddress(c.X))
case 0x59:
fmt.Printf("EOR $%X,Y\n", absoluteIndexedAddress(c.Y))
case 0x41:
fmt.Printf("EOR ($%X,X)\n", indexedIndirectAddress())
case 0x51:
fmt.Printf("EOR ($%X),Y\n", indirectIndexedAddress())
// DEC
case 0xc6:
fmt.Printf("DEC $%X\n", zeroPageAddress())
case 0xd6:
fmt.Printf("DEC $%X,X\n", zeroPageIndexedAddress(c.X))
case 0xce:
fmt.Printf("DEC $%X\n", absoluteAddress())
case 0xde:
fmt.Printf("DEC $%X,X\n", absoluteIndexedAddress(c.X))
// INC
case 0xe6:
fmt.Printf("INC $%X\n", zeroPageAddress())
case 0xf6:
fmt.Printf("INC $%X,X\n", zeroPageIndexedAddress(c.X))
case 0xee:
fmt.Printf("INC $%X\n", absoluteAddress())
case 0xfe:
fmt.Printf("INC $%X,X\n", absoluteIndexedAddress(c.X))
// BRK
case 0x00:
// RTI
case 0x40:
// RTS
case 0x60:
// NOP
case 0xea:
// LSR
case 0x4a:
fmt.Println("LSR A")
case 0x46:
fmt.Printf("LSR $%X\n", zeroPageAddress())
case 0x56:
fmt.Printf("LSR $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x4e:
fmt.Printf("LSR $%X\n", absoluteAddress())
case 0x5e:
fmt.Printf("LSR $%X,X\n", absoluteIndexedAddress(c.X))
// ASL
case 0x0a:
fmt.Println("ASL A")
case 0x06:
fmt.Printf("ASL $%X\n", zeroPageAddress())
case 0x16:
fmt.Printf("ASL $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x0e:
fmt.Printf("ASL $%X\n", absoluteAddress())
case 0x1e:
fmt.Printf("ASL $%X,X\n", absoluteIndexedAddress(c.X))
// ROL
case 0x2a:
fmt.Println("ROL A")
case 0x26:
fmt.Printf("ROL $%X\n", zeroPageAddress())
case 0x36:
fmt.Printf("ROL $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x2e:
fmt.Printf("ROL $%X\n", absoluteAddress())
case 0x3e:
fmt.Printf("ROL $%X,X\n", absoluteIndexedAddress(c.X))
// ROR
case 0x6a:
fmt.Println("ROR A")
case 0x66:
fmt.Printf("ROR $%X\n", zeroPageAddress())
case 0x76:
fmt.Printf("ROR $%X,X\n", zeroPageIndexedAddress(c.X))
case 0x6e:
fmt.Printf("ROR $%X\n", absoluteAddress())
case 0x7e:
fmt.Printf("ROR $%X,X\n", absoluteIndexedAddress(c.X))
// BIT
case 0x24:
fmt.Printf("BIT $%X\n", zeroPageAddress())
case 0x2c:
fmt.Printf("BIT $%X\n", absoluteAddress())
Jump to Line
Something went wrong with that request. Please try again.