51单片机做9999秒倒计时怎么原理图怎么做啊还要程序答:include<reg51.h>#include "intrins.h"#include "absacc.h"#define uchar unsigned charuchar code ledtab[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x40,0xff};//0-9unsigned char sec=0,dat=0,scanled;unsigned char key=0,mode,time; unsigned char disdat[4];...