说明：  4×4矩阵键盘识别处理,键盘处理程序的任务是：确定有无键按下，判断哪一个键按下，键的功能是什么；还要消除按键在闭合或断开时的抖动。两个并行口中，一个输出扫描码，使按键逐行动态接地，另一个并行口输入按键状态，由行扫描值和回馈信号共同形成键编码而识别按键，通过软件查表，查出该键的功能。
(4 × 4 matrix keyboard recognition processing, the keyboard handler task is: to determine whether the key press, to determine which one key press, what key features are would also like to eliminate the disconnect button when in the closed or jitter. Population both in parallel, an output scan code, line by line so that the dynamic ground button, and the other parallel port status input keys from the line scan values and the formation of a common feedback signal coding and identification of key buttons, through the software look-up table for identifying the key function.)