说明：  8051单片机内部定时器的重叠使用。在某些情况下，两个定时器在程序中都投入使用，由于定时时间长（如1min以上或更长），使两个定时器定时出现重叠时间，即t0定时还未完成，t1也进入定时。如果在软件上处理不好两个定时器间的关系，程序就不可能正常执行下去。
(8051 use an internal timer overlap. In some cases, the two timers in the proceedings are put into use, as from time to time a long time (for example, more than 1min or longer), so that the two overlapping time timer timing, that is, from time to time t0 has not yet been completed, t1 also entered from time to time. If the software can not be handled properly the relationship between the two timer, the program can not continue normal execution.)