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FruitMachine-Swift
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passes Klaus tests up to the ADC test - not sure why yet

This commit is contained in:
Luigi Thirty 2017-07-25 19:32:41 -04:00
parent a10296d118
commit 4a15c6aff5
5 changed files with 189 additions and 71 deletions
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17
FruitMachine/DebuggerCommands.swift
View File

@ -57,14 +57,19 @@ class DebuggerCommands: NSObject {
static func bpset(state: CPU, parameters: [String]) -> String {
var output = ""
let val = UInt16(parameters[0])
if(val != nil) {
state.breakpoints.append(val!)
output += "Breakpoint added at $\(val!.asHexString())."
if(parameters.count > 0) {
let val = UInt16(parameters[0], radix: 16)
if(val != nil) {
state.breakpoints.append(val!)
output += "Breakpoint added at $\(val!.asHexString())."
}
else {
output += "Usage: bpset <address>"
}
}
else {
output += "Usage: bpadd <address>"
output += "Usage: bpset <address>"
}
return output

4
FruitMachine/DebuggerViewController.swift
View File

@ -60,10 +60,10 @@ class DebuggerViewController: NSViewController {
cpuInstance.performReset()
cpuInstance.program_counter = 0x400 //entry point for the test program
updateCPUStatusFields()
disassembly = cpuInstance.disassemble(fromAddress: 0, length: 40000)
disassembly = cpuInstance.disassemble(fromAddress: 0, length: 65000)
debuggerTableView.reloadData()
cpuInstance.breakpoints.append(0x94B) //failing at 0x36AC - JSR test. some stack problem
cpuInstance.breakpoints.append(0x34E8) //failing at $34FD SBC test
// Do any additional setup after loading the view.
}

2
FruitMachine/M6502/CPU.swift
View File

@ -212,7 +212,7 @@ class CPU: NSObject {
self.branch_was_taken = false
}
if(operation!.mnemonic != "JMP" && operation!.mnemonic != "JSR") {
if(operation!.mnemonic != "JMP" && operation!.mnemonic != "JSR" && operation!.mnemonic != "BRK" && operation!.mnemonic != "RTI") {
self.program_counter = UInt16(Int(self.program_counter) + operation!.bytes)
}
}

19
FruitMachine/M6502/CPUInstructions.swift
View File

@ -56,6 +56,15 @@ let InstructionTable: [UInt8:CPUInstruction] = [
0x61: CPUInstruction(mnemonic: "ADC", cycles: 6, bytes: 2, addressingMode: .indexed_indirect, action: Opcodes.ADC),
0x71: CPUInstruction(mnemonic: "ADC", cycles: 5, bytes: 2, addressingMode: .indirect_indexed, action: Opcodes.ADC),
0xE9: CPUInstruction(mnemonic: "SBC", cycles: 2, bytes: 2, addressingMode: .immediate, action: Opcodes.SBC),
0xE5: CPUInstruction(mnemonic: "SBC", cycles: 3, bytes: 2, addressingMode: .zeropage, action: Opcodes.SBC),
0xF5: CPUInstruction(mnemonic: "SBC", cycles: 4, bytes: 2, addressingMode: .zeropage_indexed_x, action: Opcodes.SBC),
0xED: CPUInstruction(mnemonic: "SBC", cycles: 4, bytes: 3, addressingMode: .absolute, action: Opcodes.SBC),
0xFD: CPUInstruction(mnemonic: "SBC", cycles: 4, bytes: 3, addressingMode: .absolute_indexed_x, action: Opcodes.SBC),
0xF9: CPUInstruction(mnemonic: "SBC", cycles: 4, bytes: 3, addressingMode: .absolute_indexed_y, action: Opcodes.SBC),
0xE1: CPUInstruction(mnemonic: "SBC", cycles: 6, bytes: 2, addressingMode: .indexed_indirect, action: Opcodes.SBC),
0xF1: CPUInstruction(mnemonic: "SBC", cycles: 5, bytes: 2, addressingMode: .indirect_indexed, action: Opcodes.SBC),
//Boolean operators
0x09: CPUInstruction(mnemonic: "ORA", cycles: 2, bytes: 2, addressingMode: .immediate, action: Opcodes.ORA),
0x05: CPUInstruction(mnemonic: "ORA", cycles: 3, bytes: 2, addressingMode: .zeropage, action: Opcodes.ORA),
@ -106,11 +115,11 @@ let InstructionTable: [UInt8:CPUInstruction] = [
0x2E: CPUInstruction(mnemonic: "ROL", cycles: 6, bytes: 3, addressingMode: .absolute, action: Opcodes.ROL),
0x3E: CPUInstruction(mnemonic: "ROL", cycles: 7, bytes: 3, addressingMode: .absolute_indexed_x, action: Opcodes.ROL),
0x6A: CPUInstruction(mnemonic: "ROL", cycles: 2, bytes: 1, addressingMode: .accumulator, action: Opcodes.ROR),
0x66: CPUInstruction(mnemonic: "ROL", cycles: 5, bytes: 2, addressingMode: .zeropage, action: Opcodes.ROR),
0x76: CPUInstruction(mnemonic: "ROL", cycles: 6, bytes: 2, addressingMode: .zeropage_indexed_x, action: Opcodes.ROR),
0x6E: CPUInstruction(mnemonic: "ROL", cycles: 6, bytes: 3, addressingMode: .absolute, action: Opcodes.ROR),
0x7E: CPUInstruction(mnemonic: "ROL", cycles: 7, bytes: 3, addressingMode: .absolute_indexed_x, action: Opcodes.ROR),
0x6A: CPUInstruction(mnemonic: "ROR", cycles: 2, bytes: 1, addressingMode: .accumulator, action: Opcodes.ROR),
0x66: CPUInstruction(mnemonic: "ROR", cycles: 5, bytes: 2, addressingMode: .zeropage, action: Opcodes.ROR),
0x76: CPUInstruction(mnemonic: "ROR", cycles: 6, bytes: 2, addressingMode: .zeropage_indexed_x, action: Opcodes.ROR),
0x6E: CPUInstruction(mnemonic: "ROR", cycles: 6, bytes: 3, addressingMode: .absolute, action: Opcodes.ROR),
0x7E: CPUInstruction(mnemonic: "ROR", cycles: 7, bytes: 3, addressingMode: .absolute_indexed_x, action: Opcodes.ROR),
//INC/DEC
0xC6: CPUInstruction(mnemonic: "DEC", cycles: 5, bytes: 2, addressingMode: .zeropage, action: Opcodes.DEC),

218
FruitMachine/M6502/Opcodes.swift
View File

@ -31,8 +31,8 @@ extension CPU {
let low = UInt8(data & 0x00FF)
let high = UInt8((data & 0xFF00) >> 8)
pushByte(data: low)
pushByte(data: high)
pushByte(data: low)
}
func stackPointerAsUInt16() -> UInt16 {
@ -43,11 +43,11 @@ extension CPU {
let distance = Int8(bitPattern: getOperandByte())
if(distance < 0) {
if((program_counter & 0x00FF) - UInt16(abs(Int16(distance))) > 0x8000) {
if((program_counter & 0x00FF) &- UInt16(abs(Int16(distance))) > 0x8000) {
page_boundary_crossed = true
}
} else {
if((program_counter & 0x00FF) + UInt16(abs(Int16(distance))) > 0x0100) {
if((program_counter & 0x00FF) &+ UInt16(abs(Int16(distance))) > 0x0100) {
page_boundary_crossed = true
}
}
@ -76,26 +76,26 @@ func getOperandByteForAddressingMode(state: CPU, mode: AddressingMode) -> UInt8
case .zeropage:
return state.memoryInterface.readByte(offset: UInt16(0x0000 + state.getOperandByte()))
case .zeropage_indexed_x:
return state.memoryInterface.readByte(offset: UInt16(state.getOperandByte() + state.index_x) & 0x00FF)
return state.memoryInterface.readByte(offset: UInt16(state.getOperandByte() &+ state.index_x) & 0x00FF)
case .zeropage_indexed_y:
return state.memoryInterface.readByte(offset: UInt16(state.getOperandByte() + state.index_y) & 0x00FF)
return state.memoryInterface.readByte(offset: UInt16(state.getOperandByte() &+ state.index_y) & 0x00FF)
case .absolute:
let word: UInt16 = state.getOperandWord()
return state.memoryInterface.readByte(offset: word)
case .absolute_indexed_x:
return state.memoryInterface.readByte(offset: state.getOperandWord() + UInt16(state.index_x))
return state.memoryInterface.readByte(offset: state.getOperandWord() &+ UInt16(state.index_x))
case .absolute_indexed_y:
return state.memoryInterface.readByte(offset: state.getOperandWord() + UInt16(state.index_y))
return state.memoryInterface.readByte(offset: state.getOperandWord() &+ UInt16(state.index_y))
case .indexed_indirect:
let zp: UInt8 = state.memoryInterface.readByte(offset: UInt16(state.getOperandByte() + state.index_x))
let zp: UInt8 = state.memoryInterface.readByte(offset: UInt16(state.program_counter + 1))
//read from (ZP)
let pointer: UInt16 = state.memoryInterface.readWord(offset: UInt16(zp))
let pointer: UInt16 = state.memoryInterface.readWord(offset: UInt16(zp &+ state.index_x))
return state.memoryInterface.readByte(offset: pointer)
case .indirect_indexed:
let zp: UInt8 = state.memoryInterface.readByte(offset: UInt16(state.getOperandByte()))
let pointer: UInt16 = state.memoryInterface.readWord(offset: UInt16(zp)) + UInt16(state.index_y)
let zp: UInt8 = state.memoryInterface.readByte(offset: UInt16(state.program_counter + 1))
let pointer: UInt16 = state.memoryInterface.readWord(offset: UInt16(zp)) &+ UInt16(state.index_y)
return state.memoryInterface.readByte(offset: pointer)
default:
print("Called getOperand: UInt8 on an instruction that expects a UInt16.")
@ -117,19 +117,50 @@ func getOperandWordForAddressingMode(state: CPU, mode: AddressingMode) -> UInt16
case .indirect:
return state.memoryInterface.readWord(offset: state.getOperandWord())
case .indexed_indirect:
let zp: UInt8 = state.memoryInterface.readByte(offset: UInt16(state.getOperandByte() + state.index_x))
let zp: UInt8 = state.memoryInterface.readByte(offset: UInt16(state.program_counter + 1))
//read from (ZP)
let pointer: UInt16 = state.memoryInterface.readWord(offset: UInt16(zp))
return state.memoryInterface.readWord(offset: pointer)
let pointer: UInt16 = state.memoryInterface.readWord(offset: UInt16(zp &+ state.index_x))
return pointer
case .indirect_indexed:
let zp: UInt8 = state.memoryInterface.readByte(offset: UInt16(state.getOperandByte()))
let pointer: UInt16 = state.memoryInterface.readWord(offset: UInt16(zp)) + UInt16(state.index_y)
return state.memoryInterface.readWord(offset: pointer)
let zp: UInt8 = state.memoryInterface.readByte(offset: UInt16(state.program_counter + 1))
let pointer: UInt16 = state.memoryInterface.readWord(offset: UInt16(zp)) &+ UInt16(state.index_y)
return pointer
default:
print("Called getOperand: UInt16 on an instruction that expects a UInt8. Address: \(state.program_counter.asHexString())")
return 0
}
}
func getOperandAddressForAddressingMode(state: CPU, mode: AddressingMode) -> UInt16 {
//Function that will provide a 16-bit operand to instructions.
//All instructions have 2 data bytes, little-endian.
switch(mode) {
case .zeropage:
return UInt16(0x0000 + (state.memoryInterface.readByte(offset: state.program_counter + 1)))
case .zeropage_indexed_x:
return UInt16(0x0000 + (state.memoryInterface.readByte(offset: state.program_counter + 1) + state.index_x))
case .zeropage_indexed_y:
return UInt16(0x0000 + (state.memoryInterface.readByte(offset: state.program_counter + 1) + state.index_y))
case .absolute:
return state.getOperandWord()
case .absolute_indexed_x:
return state.getOperandWord() + state.index_x
case .absolute_indexed_y:
return state.getOperandWord() + state.index_y
case .indexed_indirect:
let zp: UInt8 = state.memoryInterface.readByte(offset: UInt16(state.program_counter + 1))
//read from (ZP)
let pointer: UInt16 = state.memoryInterface.readWord(offset: UInt16(zp &+ state.index_x))
return pointer
case .indirect_indexed:
let zp: UInt8 = state.memoryInterface.readByte(offset: UInt16(state.program_counter + 1))
let pointer: UInt16 = state.memoryInterface.readWord(offset: UInt16(zp)) &+ UInt16(state.index_y)
return pointer
default:
print("Called getOperand: UInt16 on an instruction that expects a UInt8. Address: \(state.program_counter.asHexString())")
return 0
}
}
func hex2bcd(hex: UInt8) -> UInt8 {
@ -143,6 +174,9 @@ func hex2bcd(hex: UInt8) -> UInt8 {
class Opcodes: NSObject {
static func _Add(state: CPU, operand: UInt8) {
if(state.accumulator == 0xFF) {
_ = 1
}
var t16: UInt16 = UInt16(state.accumulator &+ operand) + UInt16((state.status_register.carry ? UInt8(1) : UInt8(0)))
let t8: UInt8 = UInt8(t16 & 0xFF)
@ -209,13 +243,20 @@ class Opcodes: NSObject {
static func STA(state: CPU, addressingMode: AddressingMode) -> Void {
let address: UInt16
if(addressingMode == .zeropage || addressingMode == .zeropage_indexed_x) {
if(addressingMode == .zeropage) {
address = AddressConversions.zeroPageAsUInt16(address: state.getOperandByte())
state.memoryInterface.writeByte(offset: address, value: state.accumulator)
}
else if (addressingMode == .absolute || addressingMode == .absolute_indexed_x || addressingMode == .absolute_indexed_y || addressingMode == .indexed_indirect || addressingMode == .indirect_indexed) {
address = state.getOperandWord()
else if(addressingMode == .zeropage_indexed_x) {
address = AddressConversions.zeroPageAsUInt16(address: state.getOperandByte() &+ state.index_x)
state.memoryInterface.writeByte(offset: address, value: state.accumulator)
}
else if (addressingMode == .absolute || addressingMode == .absolute_indexed_x || addressingMode == .absolute_indexed_y) {
address = getOperandWordForAddressingMode(state: state, mode: addressingMode)
state.memoryInterface.writeByte(offset: address, value: state.accumulator)
}
else if(addressingMode == .indexed_indirect || addressingMode == .indirect_indexed) {
address = getOperandWordForAddressingMode(state: state, mode: addressingMode)
state.memoryInterface.writeByte(offset: address, value: state.accumulator)
}
else {
@ -227,10 +268,13 @@ class Opcodes: NSObject {
static func STX(state: CPU, addressingMode: AddressingMode) -> Void {
let address: UInt16
if(addressingMode == .zeropage || addressingMode == .zeropage_indexed_y) {
if(addressingMode == .zeropage) {
address = AddressConversions.zeroPageAsUInt16(address: state.getOperandByte())
state.memoryInterface.writeByte(offset: address, value: state.index_x)
}
else if(addressingMode == .zeropage_indexed_y) {
address = AddressConversions.zeroPageAsUInt16(address: state.getOperandByte() &+ state.index_y)
state.memoryInterface.writeByte(offset: address, value: state.index_x)
}
else if (addressingMode == .absolute) {
address = state.getOperandWord()
@ -245,11 +289,15 @@ class Opcodes: NSObject {
static func STY(state: CPU, addressingMode: AddressingMode) -> Void {
let address: UInt16
if(addressingMode == .zeropage || addressingMode == .zeropage_indexed_x) {
if(addressingMode == .zeropage) {
address = AddressConversions.zeroPageAsUInt16(address: state.getOperandByte())
state.memoryInterface.writeByte(offset: address, value: state.index_y)
}
else if(addressingMode == .zeropage_indexed_x) {
address = AddressConversions.zeroPageAsUInt16(address: state.getOperandByte() &+ state.index_x)
state.memoryInterface.writeByte(offset: address, value: state.index_y)
}
else if (addressingMode == .absolute) {
address = state.getOperandWord()
state.memoryInterface.writeByte(offset: address, value: state.index_y)
@ -322,12 +370,11 @@ class Opcodes: NSObject {
var val: UInt8
if(addressingMode == .zeropage || addressingMode == .zeropage_indexed_x) {
address = AddressConversions.zeroPageAsUInt16(address: state.getOperandByte())
address = getOperandAddressForAddressingMode(state: state, mode: addressingMode)
val = state.memoryInterface.readByte(offset: address)
}
else if (addressingMode == .absolute || addressingMode == .absolute_indexed_x) {
address = state.getOperandWord()
address = getOperandAddressForAddressingMode(state: state, mode: addressingMode)
val = state.memoryInterface.readByte(offset: address)
}
else {
@ -347,16 +394,15 @@ class Opcodes: NSObject {
var val: UInt8
if(addressingMode == .zeropage || addressingMode == .zeropage_indexed_x) {
address = AddressConversions.zeroPageAsUInt16(address: state.getOperandByte())
address = getOperandAddressForAddressingMode(state: state, mode: addressingMode)
val = state.memoryInterface.readByte(offset: address)
}
else if (addressingMode == .absolute || addressingMode == .absolute_indexed_x) {
address = state.getOperandWord()
address = getOperandAddressForAddressingMode(state: state, mode: addressingMode)
val = state.memoryInterface.readByte(offset: address)
}
else {
print("Illegal addressing mode for INC")
print("Illegal addressing mode for DEC")
return
}
@ -422,21 +468,32 @@ class Opcodes: NSObject {
let operand = getOperandByteForAddressingMode(state: state, mode: addressingMode)
let data = state.accumulator & operand
state.updateZeroFlag(value: data)
state.updateNegativeFlag(value: operand)
state.status_register.overflow = (state.accumulator & UInt8(0x40)) == 0x40
state.status_register.zero = data == 0 ? true : false
state.status_register.negative = (operand & 0x80) == 0x80 ? true : false
state.status_register.overflow = (operand & UInt8(0x40)) == 0x40
}
static func ASL(state: CPU, addressingMode: AddressingMode) -> Void {
let operand: UInt8
if(addressingMode == .implied) {
if(addressingMode == .accumulator) {
operand = state.accumulator
state.status_register.carry = ((operand & 0x80) == 0x80)
state.accumulator = (state.accumulator &<< 1) & 0xFE
state.updateZeroFlag(value: state.accumulator)
state.updateNegativeFlag(value: state.accumulator)
} else {
}
else if(addressingMode == .zeropage || addressingMode == .zeropage_indexed_x)
{
let address = getOperandAddressForAddressingMode(state: state, mode: addressingMode)
var data = state.memoryInterface.readByte(offset: address)
state.status_register.carry = (data & 0x80) == 0x80
data = (data &<< 1) & 0xFE
state.memoryInterface.writeByte(offset: address, value: data)
state.updateZeroFlag(value: data)
state.updateNegativeFlag(value: data)
}
else {
let address = getOperandWordForAddressingMode(state: state, mode: addressingMode)
var data = state.memoryInterface.readByte(offset: address)
state.status_register.carry = (data & 0x80) == 0x80
@ -450,13 +507,24 @@ class Opcodes: NSObject {
static func LSR(state: CPU, addressingMode: AddressingMode) -> Void {
let operand: UInt8
if(addressingMode == .implied) {
if(addressingMode == .accumulator) {
operand = state.accumulator
state.status_register.carry = ((operand & 0x01) == 0x01)
state.accumulator = (state.accumulator &>> 1) & 0x7F
state.updateZeroFlag(value: state.accumulator)
state.status_register.negative = false
} else {
}
else if(addressingMode == .zeropage || addressingMode == .zeropage_indexed_x)
{
let address = getOperandAddressForAddressingMode(state: state, mode: addressingMode)
var data = state.memoryInterface.readByte(offset: address)
state.status_register.carry = (data & 0x01) == 0x01
data = (data &>> 1) & 0x7F
state.memoryInterface.writeByte(offset: address, value: data)
state.updateZeroFlag(value: data)
state.updateNegativeFlag(value: data)
}
else {
let address = getOperandWordForAddressingMode(state: state, mode: addressingMode)
var data = state.memoryInterface.readByte(offset: address)
state.status_register.carry = (data & 0x01) == 0x01
@ -470,25 +538,41 @@ class Opcodes: NSObject {
static func ROL(state: CPU, addressingMode: AddressingMode) -> Void {
let operand: UInt8
if(addressingMode == .implied) {
if(addressingMode == .accumulator) {
operand = state.accumulator
state.accumulator = (state.accumulator &<< 1) & 0xFE
state.accumulator = state.accumulator | (state.status_register.carry ? 0x01 : 0x00)
state.status_register.carry = ((operand & 0x80) == 0x80)
state.updateZeroFlag(value: state.accumulator)
state.status_register.zero = state.accumulator == 0 ? true : false
state.status_register.negative = (state.accumulator & 0x80) == 0x80
} else {
let address = getOperandWordForAddressingMode(state: state, mode: addressingMode)
} else if(addressingMode == .zeropage || addressingMode == .zeropage_indexed_x)
{
let address = getOperandAddressForAddressingMode(state: state, mode: addressingMode)
var data = state.memoryInterface.readByte(offset: address)
let t = (data & 0x80) == 0x80 ? true : false
data = (data &<< 1) & 0xFE
data = data | (state.status_register.carry ? 0x01 : 0x00)
state.memoryInterface.writeByte(offset: address, value: data)
state.status_register.carry = (data & 0x80) == 0x80
state.updateZeroFlag(value: data)
state.status_register.carry = t
state.status_register.zero = data == 0 ? true : false
state.status_register.negative = (data & 0x80) == 0x80
}
else
{
let address = getOperandWordForAddressingMode(state: state, mode: addressingMode)
var data = state.memoryInterface.readByte(offset: address)
let t = (data & 0x80) == 0x80 ? true : false
data = (data &<< 1) & 0xFE
data = data | (state.status_register.carry ? 0x01 : 0x00)
state.memoryInterface.writeByte(offset: address, value: data)
state.status_register.carry = t
state.status_register.zero = data == 0 ? true : false
state.status_register.negative = (data & 0x80) == 0x80
}
}
@ -496,23 +580,42 @@ class Opcodes: NSObject {
static func ROR(state: CPU, addressingMode: AddressingMode) -> Void {
let operand: UInt8
if(addressingMode == .implied) {
if(addressingMode == .accumulator) {
operand = state.accumulator
state.status_register.carry = ((operand & 0x01) == 0x01)
state.accumulator = (state.accumulator &>> 1) & 0x7F
state.accumulator = state.accumulator | (state.status_register.carry ? 0x80 : 0x00)
state.updateZeroFlag(value: state.accumulator)
state.status_register.negative = (state.accumulator & 0x80) == 0x80
} else {
let address = getOperandWordForAddressingMode(state: state, mode: addressingMode)
var data = state.memoryInterface.readByte(offset: address)
state.status_register.carry = (data & 0x01) == 0x01
state.status_register.carry = ((operand & 0x01) == 0x01)
state.status_register.zero = state.accumulator == 0 ? true : false
state.status_register.negative = (state.accumulator & 0x80) == 0x80
}
else if(addressingMode == .zeropage || addressingMode == .zeropage_indexed_x)
{
let address = getOperandAddressForAddressingMode(state: state, mode: addressingMode)
var data = state.memoryInterface.readByte(offset: address)
let t = (data & 0x01) == 0x01 ? true : false
data = (data &>> 1) & 0x7F
data = data | (state.status_register.carry ? 0x80 : 0x00)
state.memoryInterface.writeByte(offset: address, value: data)
state.updateZeroFlag(value: data)
state.status_register.carry = t
state.status_register.zero = data == 0 ? true : false
state.status_register.negative = (data & 0x80) == 0x80
}
else
{
let address = getOperandWordForAddressingMode(state: state, mode: addressingMode)
var data = state.memoryInterface.readByte(offset: address)
let t = (data & 0x01) == 0x01 ? true : false
data = (data &>> 1) & 0x7F
data = data | (state.status_register.carry ? 0x80 : 0x00)
state.memoryInterface.writeByte(offset: address, value: data)
state.status_register.carry = t
state.status_register.zero = data == 0 ? true : false
state.status_register.negative = (data & 0x80) == 0x80
}
}
@ -543,7 +646,7 @@ class Opcodes: NSObject {
}
static func SED(state: CPU, addressingMode: AddressingMode) -> Void {
state.status_register.carry = true
state.status_register.decimal = true
}
//Stack instructions
@ -638,12 +741,12 @@ class Opcodes: NSObject {
}
static func JSR(state: CPU, addressingMode: AddressingMode) -> Void {
state.pushWord(data: state.program_counter - 1)
state.pushWord(data: state.program_counter + 2)
state.program_counter = state.getOperandWord()
}
static func RTS(state: CPU, addressingMode: AddressingMode) -> Void {
state.program_counter = state.popWord() + 1
state.program_counter = state.popWord()
}
static func RTI(state: CPU, addressingMode: AddressingMode) -> Void {
@ -655,8 +758,9 @@ class Opcodes: NSObject {
static func BRK(state: CPU, addressingMode: AddressingMode) -> Void {
var sr = state.status_register
sr.brk = true //BRK pushes B as true
state.pushWord(data: state.program_counter)
state.pushWord(data: state.program_counter + 2)
state.pushByte(data: sr.asByte())
state.status_register.irq_disable = true //BRK disables interrupts before transferring control
state.program_counter = state.memoryInterface.readWord(offset: 0xFFFE)
}