计时器，并使用数码管来显示。计数程序产生一个６位的十进制的计数器，个位的计数为 100ms, 个位计到９进位，所以十位的计数为１s, 百位为 10s, 依次类推(A timer, and a digital tube to display.The counting program produces a 6 bit decimal counter, the number of bits is 100ms, the bit is 9, so the count of the ten bits is