pushed a byte onto stack

def push_byte(self, stack_pointer, byte):
        """ pushed a byte onto stack """
        # FIXME: self.system_stack_pointer -= 1
        stack_pointer.decrement(1)
        addr = stack_pointer.value

#        log.info(
#         log.error(
#            "%x|\tpush $%x to %s stack at $%x\t|%s",
#            self.last_op_address, byte, stack_pointer.name, addr,
#            self.cfg.mem_info.get_shortest(self.last_op_address)
#        )
        self.memory.write_byte(addr, byte)