利用实验机上提供的8279键盘电路，数码显示电路，设计一个电子钟，用小键盘控制电子钟的启停及初始值的预值。-experimental plane on the 8279 keyboard circuit, a digital display circuit, design an electronic bell, the small keyboard control clock off of the initial value and the value in advance.

1.掌握在8051系统中扩展8279键盘显示接口的方法。 2.掌握8279工作原理和编程方法。(49/5000 1. Master the method of extending 8279 keyboard display interface in 8051 system. 2. Master the working principle and programming method of 8279.)