sbit led=p1^0;
uchar a = 0;
TM0D = 0x 10;
th 1 =(65536-2000)/256;
TL 1 =(65536-2000)% 256;
et 1 = 1;EA = 1;
tr 1 = 1;
中斷程序
a++;
if(a = = 1)LED = 0;
else if(a = = 3){ a = 0;LED = 1;}