说明：  / 函数名称： keyscan 键盘扫描子程序 // 函数功能： 判断是否有键按下，有返回键值，没有返回0 // p1的高四位为列，低四位为行 P1.7 P1.6 P1.5 P1.4 P1.3 P1.2 P1.1 P1.0 // 列4 列3 列2 列1 行4 行3 行2 行1 // 过程：先根据列判断是否有键按下，没有返回0，有，则逐行扫描以确定按键所在的行，再确定按键所在列 // 从而最终确定该按键。
(/ Function name: keyboard scan subroutine keyscan// Function: to determine whether a key is pressed, the key would not return 0// p1 four column, the lower four P1.7 P1.6 P1.5 P1.4 P1.3 P1.2 P1.1 P1.0// to column 4 3 2 1 line 4 Line 3 Line 2 Line 1// process: the first column to determine whether a key is pressed, did not return, progressive scan to determine where the row of buttons, and then determine the key where the column// which ultimately determine the key.)