51单片机 – 秒表计时代码（只显示有效位）

#include <reg52.h>

sbit ADDR0 = P1^0;
sbit ADDR1 = P1^1;
sbit ADDR2 = P1^2;
sbit ADDR3 = P1^3;
sbit ENLED = P1^4;

//数码管真值表
unsigned char code LedChar[16] = {
    0xC0, 0xF9, 0xA4, 0xB0, 0x99, 0x92, 0x82, 0xF8,
    0x80, 0x90, 0x88, 0x83, 0xC6, 0xA1, 0x86, 0x8E
};
//数码管显示缓冲区，初值0xFF确保启动时都不亮
unsigned char LedBuff[6] = {
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
};
unsigned char flag1s = 0;   //1秒定时标志
unsigned int cnt = 0;       //记录T0中断次数
unsigned char i = 0;        //动态扫描的索引

void main(){
    unsigned long sec = 0;
    unsigned char buff[6];  //中间转换缓冲区
    char j = 0;

    EA = 1;                 //使能总中断
    ADDR3 = 1;              //因为需要动态改变ADDR0-2的值，所以ADDR0-2不需要再初始化了
    ENLED = 0;              //使能U3
    TMOD &= 0xF0;           //设置Timer0工作模式1
    TMOD |= 0x01;
    TH0 = 0xFC;             //为Timer0赋初值0xFC67，定时1ms
    TL0 = 0x67;
    ET0 = 1;                //使能Timer0中断
    TR0 = 1;                //启动Timer0

    while(1){
        if(flag1s){         //判断1秒定时标志
            flag1s = 0;     //1秒定时标志清零
            sec++;          //秒计数自加1
            //将sec按十进制位从低到高依次提取到buff数组中
            buff[0] = sec % 10;
            buff[1] = sec / 10 % 10;
            buff[2] = sec / 100 % 10;
            buff[3] = sec / 1000 % 10;
            buff[4] = sec / 10000 % 10;
            buff[5] = sec / 100000 % 10;
            //从最高为开始，遇到0不显示(赋值0xFF)，遇到非0退出循环
            for(j = 5; j >= 1; j--){
                if(buff[j] == 0){
                    LedBuff[j] = 0xFF;
                }
                else{
                    break;
                }
            }
            //将剩余的有效数字位如实转换，for()起始未对j操作，j即保持上个循环结束时的值
            for( ; j >= 0; j--){
                LedBuff[j] = LedChar[buff[j]];
            }
        }
    }
}
/* 定时器0中断服务函数 */
void interruptTimer0() interrupt 1{
    TH0 = 0xFC;         //重新加载初值
    TL0 = 0x67;
    cnt++;              //中断次数计数值加1
    if(cnt >= 1000){    //中断1000次即1秒
        cnt = 0;        //清零计数值以重新开始下1秒计时
        flag1s = 1;     //设置1秒定时标志为1
    }
    //以下代码完成数码管动态扫描刷新
    P0 = 0xFF;          //显示消隐
    switch(i){
        case 0: ADDR2 = 0; ADDR1 = 0; ADDR0 = 0; i++; P0 = LedBuff[0]; break;
        case 1: ADDR2 = 0; ADDR1 = 0; ADDR0 = 1; i++; P0 = LedBuff[1]; break;
        case 2: ADDR2 = 0; ADDR1 = 1; ADDR0 = 0; i++; P0 = LedBuff[2]; break;
        case 3: ADDR2 = 0; ADDR1 = 1; ADDR0 = 1; i++; P0 = LedBuff[3]; break;
        case 4: ADDR2 = 1; ADDR1 = 0; ADDR0 = 0; i++; P0 = LedBuff[4]; break;
        case 5: ADDR2 = 1; ADDR1 = 0; ADDR0 = 1; i = 0; P0 = LedBuff[5]; break;
        default: break;
    }
}