Dùng modul i2c giao tiếp ds1307 cần giúp đỡ!

[lequocbao]

mình sử dụng modul i2c giao tiếp giữa pic16f877a và ds1307 hiển thị giờ phút giây.Code như bên dưới nhưng khi chạy thì chỉ hiện toàn số 0 trên led 7 đoạn.Nhờ các bạn xem giúp đoạn code xem có sai chổ nào không?
[code/]#include<16f877a.h>
#fuses HS,NOWDT,NOLVP,NOPROTECT
#use delay(clock=4000000)
#use i2c(master,slow,sda=pin_c4,scl=pin_c3)
#use fast_io(a)
#use fast_io(b)
#use fast_io(d)
#use fast_io(e)

#define so0 0x00
#define so1 0x10
#define so2 0x20//00100000
#define so3 0x30
#define so4 0x40
#define so5 0x50
#define so6 0x60
#define so7 0x70
#define so8 0x80
#define so9 0x90
byte const digit[] = {so0,so1,so2,so3,so4,so5,so6,so7,so8,so9};

#define led1 0xfe//0xf7
#define led2 0xfd//0xfb
#define led3 0xfb//0xfd
#define led4 0xf7//0xfe
#define led5 0xef
#define led6 0xdf
#define led7 0xbf
#define led8 0x7f
void led_scan(int value,int address);
int8 hour;
int8 minute;
int8 second;
int8 dv_second;
int8 chuc_second;
int8 dv_minute;
int8 chuc_minute;
int8 dv_hour;
int8 chuc_hour;

void main()
{
set_tris_a(0x00);//cau hinh portA la cong xuat
set_tris_b(0x00);//cau hinh portB la cong nhap
set_tris_e(0x70);//cau hinh portE la cong nhap
set_tris_d(0x0f);

do
{
i2c_start();
i2c_write(0xD0);
i2c_write(0x00);
i2c_stop();
i2c_start();
i2c_write(0xD1);
second=i2c_read(1);
minute=i2c_read(1);
hour=i2c_read(0);
i2c_stop();

//khu vuc convert BCD to Binary--------------
dv_second=second & 0x0f;//lay 4 bit thap ra phut hang don vi
chuc_second=(second & 0x70)>>4;//lay 3 bit cao roi dich phai 4 bit thi ra hang chuc

dv_minute=minute & 0x0f;//lay 4 bit thap ra phut hang don vi
chuc_minute=(minute & 0x70)>>4;//lay 3 bit cao roi dich phai 4 bit thi ra hang chuc

dv_hour=hour & 0x0f;//lay 4 bit thap ra phut hang don vi
chuc_hour=(hour & 0x30)>>4;//lay 2 bit cao roi dich phai 4 bit thi ra hang chuc
//ket thuc khu vuc convert BCD to Binary-------------------

led_scan(chuc_hour,led1);
led_scan(dv_hour,led2);
led_scan(chuc_minute,led3);
led_scan(dv_minute,led4);
led_scan(chuc_second,led5);
led_scan(dv_second,led6);
}while(true);
}//ket thuc ham main()----------------------------------------------------------

void led_scan(int value,int address)//------------------------------------------
{
output_b(address);
output_d(digit[value]);
delay_ms(1);
output_b(0xff);
}//ket thuc ham led_scan()------------------------------------------------------[/code]