设计两个单片机实现双机通讯功能。通讯方式自选，需要有数据校正功能，校正方式可自己设计。

一台单片机作为99秒定时器，每隔一秒的时间，计时器自动加一，计时器个位满十向高位进位，累计计时99秒即清0重新计数。

另外一台单片机通过串行通讯接口与99秒定时单片机通讯。通讯单片机通过P1口外接4-5个按键，键值从P1口读入，通过串行通讯键值可传输到秒定时器单片机一端。秒定时单片机根据串行通讯传来的键值，可实现定时器的启动、停止、清零功能。-Designed to achieve double two single-chip communication. Communication demand, the need for data correction, calibration methods can be their own design. A timer chip as 99 seconds, every second of time, plus an automatic timer, the timer bit the tenth order bit, total time 99 seconds to re-count is cleared. Also a microcontroller through the serial communication interface with 99 second timer chip communication. Microcontroller through an external communication port P1 4-5 keys, key read from the P1 port, serial communication key can be transmitted through to the second end of the timer chip. Second timer chip serial communication came under the key, enabling the timer to start, stop, clear function.