def op_adc(self, value):
carry = self.reg.ps.carry
# TODO: Decimal mode removed temporarily.
result = signed_byte(value) + signed_byte(self.reg.ac) + carry
self.reg.ps.overflow = result > 127 or result < -128
self.reg.ps.carry = value + self.reg.ac + carry > 255
result &= 0xFF
self.reg.ac = result
self._set_nz_flags(self.reg.ac)
def op_branch(self, value, opcode):
flags = {
0x90: 'carry', 0xB0: 'carry',
0xD0: 'zero', 0xF0: 'zero',
0x10: 'negative', 0x30: 'negative',
0x50: 'overflow', 0x70: 'overflow',
}
cond = bool(getattr(self.reg.ps, flags[opcode]))
branch_if_true = opcode in (0xB0, 0xF0, 0x30, 0x70)
if cond == branch_if_true:
old_pc = self.reg.pc
new_pc = (self.reg.pc + signed_byte(value)) & 0xFFFF
self.reg.pc = new_pc
return 2 if (old_pc & 0xFF00) != (new_pc & 0xFF00) else 1
