对实验板上4*4矩阵键盘的16个按键S6---S21进行按键次数统计。键号06、07……21用最左边2位数码管显示，按键次数用右侧4位数码管显示。有键按下时，显示相应键号和该键累计按键次数，没键按下时，数码管不亮。（无论键号还是按键次数都用其十进制数显示。）-The experimental board 4* 4 matrix keyboard 16 keys S6--- S21 performed keystrokes statistics. No. 21 with key 06,07 ...... leftmost two digital display, keypad display to the right four times digital. When a key is pressed, displays the appropriate key number and the key is the cumulative number of keys, when no key is pressed, the LED is not lit. (Regardless of the number of keys or key numbers are displayed with their decimal number.)The experimental board 4* 4 matrix keyboard 16 keys S6--- S21 performed keystrokes statistics. No. 21 with key 06,07 ...... leftmost two digital display, keypad display to the right four times digital. When a key is pressed, displays the appropriate key number and the key is the cumulative number of keys, when no key is pressed, the LED is not lit. (Regardless of the number of keys or key numbers are displayed with their decimal number.)