def IZX(cpu: CPU6502):
t = cpu.cpu_read(cpu.state.pc)
cpu.state.pc += 1
lo = cpu.cpu_read((t + cpu.state.x) & 0x00ff)
hi = cpu.cpu_read((t + cpu.state.x + 1) & 0x00ff)
cpu.state.addr_abs = (hi << 8) | lo
return 0
def IND(cpu: CPU6502):
ptr_lo, ptr_hi = cpu.cpu_read_2(cpu.state.pc)
cpu.state.pc += 2
ptr = (ptr_hi << 8) | ptr_lo
if ptr_lo == 0x00ff: # Simulate page boundary hardware bug
cpu.state.addr_abs = (
cpu.cpu_read(ptr & 0xff00) << 8) | cpu.cpu_read(ptr + 0)
else:
cpu.state.addr_abs = (cpu.cpu_read(ptr + 1) << 8) | cpu.cpu_read(ptr +
0)
return 0
def IZY(cpu: CPU6502):
t = cpu.cpu_read(cpu.state.pc)
cpu.state.pc += 1
lo = cpu.cpu_read(t & 0x00ff)
hi = cpu.cpu_read((t + 1) & 0x00ff)
addr = ((hi << 8) | lo) + cpu.state.y
cpu.state.addr_abs = addr & 0xFFFF
if (addr & 0xff00) != (hi << 8):
return 1
else:
return 0
def REL(cpu: CPU6502):
cpu.state.addr_rel = cpu.cpu_read(cpu.state.pc)
cpu.state.pc += 1
if cpu.state.addr_rel & 0x80:
cpu.state.addr_rel |= 0xff00
return 0
def ZPY(cpu: CPU6502):
cpu.state.addr_abs = cpu.cpu_read(cpu.state.pc) + cpu.state.y
cpu.state.pc += 1
cpu.state.addr_abs &= 0x00ff
return 0
