// test5.c
// 数码管静态显示秒表的倒计时；
#include "homework4.h"

unsigned char cnt    = 0; // 定时器溢出计数
unsigned char second = 0; // 秒计数

void test5()
{
    set_38_2SEG();
    TMOD = 0x01;
    TH0  = 0x3C;
    TL0  = 0xB0;
    TR0  = 1;

    // 初始化时立即显示9
    second = 9;
    show_number(second);

    while (1) {
        if (TF0 == 1) {
            TF0 = 0;
            TH0 = 0x3C;
            TL0 = 0xB0;
            if (++cnt >= 20) {
                cnt = 0;

                second = (second > 0) ? --second : 9;
                show_number(second);
            }
        }
    }
}

void main()
{
    test5();
}