49下數至0

#include <at89x52.h>
char  seg_7_table[]={0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90};
int count=49;
int i=0,j;
char bcd[]={9,4};
char scanline[]={0xfe,0xfd};
main()
{
IE=0x8A;
TMOD=0x10;
TH0=(8192-5000)/32;
TL0=(8192-5000)%32;
TH1=(65536-50000)/256;
TL1=(65536-50000)%256;
TR0=1;
TR1=1;
while(1);
}
void T0_int(void) interrupt  1
{
TH0=(8192-5000)/32;
TL0=(8192-5000)%32;
P1=seg_7_table[bcd[j]];
P2=scanline[j];
j++;
if(j==2)
j=0;
}
void T1_int(void) interrupt  3
{
TH1=(65536-50000)/256;
TL1=(65536-50000)%256;
i++;
if(i==20)
{
i=0;
count--;
if(count<0)
{
count=49;
}
bcd[0]=count%10;
bcd[1]=count / 10;
}
}