Negate memory

def instruction_NEG_memory(self, opcode, ea, m):
        """ Negate memory """
        if opcode == 0x0 and ea == 0x0 and m == 0x0:
            self._wrong_NEG += 1
            if self._wrong_NEG > 10:
                raise RuntimeError("Wrong PC ???")
        else:
            self._wrong_NEG = 0

        r = m * -1 # same as: r = ~m + 1

#        log.debug("$%04x NEG $%02x from %04x to $%02x" % (
#             self.program_counter, m, ea, r,
#         ))
        self.clear_NZVC()
        self.update_NZVC_8(0, m, r)
        return ea, r & 0xff