Problem with Timer0 Interrupt

Hi all, I am using Timer0 as interrupt for display time on LCD. But when the interrupt occurs, it won't come back to the last executed command of interrupted. It is repeating the ISR. I am using embedded C. I don't know what is happening. I did my best. Please help me.

here is my ISR

void timer0() interrupt 1
{ TH0 = 0xFC; TL0 = 0x17; time_display(); }

Hi Saan, Where r u selecting the timer mode & why r u loading TH0 & TLO in ISR itself? And its better that avoid the function calling in ISR, instead of this better maintain flag in ISR and perform the operation in main function. Ensure that u r not using ur Timer0 any where else. Post the complete code for better answer...

Dear Abdul Hameed, Thanks for your response. My entire program contains lcd,12 bit adc, eeprom and 6 keys. It is for blood collection monitor. So when "START" key pressed, it have to display time on lcd as stop watch. At the same time i want to take readings from adc. I have used AT89c52. Here is my complete code. here i haven't included adc section.

#include <reg52.h>
#include <string.h>
#include <intrins.h>

# define uchar unsigned char
# define uint unsigned int

//EEPROM Pins
sbit CS = P3 ^ 4; //Chip Select
sbit SCK = P3 ^ 5; //Clock
sbit SDI = P3 ^ 6; //Serial Input
sbit SDO = P3 ^ 7; //Seria Output
sbit ON = P3 ^ 1; //EEPROM ON

//Keypad Pins
sbit volup = P1^0; // Volume Up Key
sbit voldn = P1^1; // Volume Down Key
sbit pause = P1^2; // Pause Key
sbit cmpup = P1^3; // Clamp Up Key
sbit cmpdn = P1^4; // Clamp Dowm Key
sbit start = P1^5; // Start Key

// LCD Pins
sbit rs = P2^0;
sbit en = P2^2; //pin enable is connected to lcd via inverter
sbit rw = P2^1;
sbit b = P0^7;

uint setvalue,ms_cnt=1,ms_sec,sec,min;
uchar p=0,st=0;

void wait_key();
void set_display(uint disp, uchar loc, uchar dig)reentrant;
void lcdcmd(uchar a);
void lcddat(uchar b);
void busy();
void lcdstr(uchar *s);
void bcm_lcd_init();
void delay();
void time_display();
void WRAL (uint Data);
void ERAL ();
void ERASE (uchar Address);
void Write (uchar Address, uint Data);
uint Read (uchar Address);
void EWEN ();
void EWDS ();
/*------------------------------------ISR-----------------------------------------

Timer 0 will start after pressing Start Key (when P1.5 = 0).
*/

void timer0() interrupt 1
{ TH0 = 0xFC; TL0 = 0x17; time_display();

}

/*------------------------------------MAIN-----------------------------------------*/
main() { P0 = 0x00; P1 = 0xFF; P2 = 0xFF; TMOD = 0x01; IE = 0x82; ON = 1; setvalue = Read (0x40); bcm_lcd_init(); set_display(setvalue,0x85,3); while(1) { wait_key();

} }

/*------------------------------------void lcdcmd(unsigned char a)-----------------------------------------*/

void lcdcmd(uchar a)
{ busy(); rs = 0; rw = 0; P0 = a; en = 0; en = 1; } /*------------------------------------void lcddat(unsigned char b)-----------------------------------------*/
void lcddat(uchar b)
{ busy(); rs = 1; rw = 0; P0 = b; en = 0; en = 1; } /*------------------------------------void busy()-----------------------------------------*/
void busy()
{ en = 0; P0 = 0xFF; rs = 0; rw = 1; while(b==1) {

en=1; en = 0; } en=1;
} /*------------------------------------void lcdstr(unsigned char *s)-----------------------------------------*/
void lcdstr(uchar *s)
{ uchar l,i; l = strlen(s); for(i=0;i<l;i++) { lcddat(*s); s++; }
} /*------------------------------------void bcm_lcd_init() -----------------------------------------*/
void bcm_lcd_init()
{ uchar i; lcdcmd(0x3C); lcdcmd(0x0E); lcdcmd(0x14); lcdcmd(0x01); lcdcmd(0x80); lcdstr("haribharath Equipments Pvt.Ltd.Mumbai"); delay(); delay();

for (i=0;i<22;i++) { delay(); lcdcmd(0x18); }

lcdcmd(0x01); lcdcmd(0x80); lcdstr("Blood Collection"); lcdcmd(0xC4); lcdstr("Monitor"); delay(); delay();

lcdcmd(0x01); lcdcmd(0x80); lcdstr("Set:0350 Cnt:0000"); lcdcmd(0xC0); lcdstr("Bat:100% 00m:00s");
} /*------------------------------------void delay()-----------------------------------------*/
void delay() { uint hi_del; for(hi_del = 0 ; hi_del < 30800 ; hi_del++);
} /*------------------------------------void wait_key()-----------------------------------------*/
void wait_key()
{ uchar key,mkey; key = P1; mkey = key&0x3f;; while(mkey!=63) { key = P1; mkey = key&0x3f; switch(mkey) { case 0x3E : if(setvalue==999) setvalue=0; else ++setvalue; set_display(setvalue,0x85,3); Write (0x40,setvalue); delay(); delay(); break;

case 0x3D : if(setvalue==0) setvalue=999; else --setvalue; set_display(setvalue,0x85,3); Write (0x40,setvalue); delay(); delay(); break;

case 0x3B : p = ~p ; delay(); delay(); if(p==255)TR0 = 0; else TR0 = 1; break; case 0x37 : break; case 0x2F : break; case 0x1F : if(st==1)break; st=1; start=0; TH0 = 0xFC; TL0 = 0x17; TR0 = 1; min=0; sec=0; set_display(min,0xC9,2); set_display(sec,0xCD,2); delay(); break; } }
}

//--------------------------------------void time_display()--------------------------------------------

void time_display() { ms_cnt++; if(ms_cnt==1000) { sec++; if(sec==60) { min++; sec=0; if(min==60)min=0; set_display(sec,0xCD,2); set_display(min,0xC9,2); } else set_display(sec,0xCD,2); ms_cnt=0; } }
/*------------------------------------void set_display()-----------------------------------------*/
void set_display(uint disp, uchar loc, uchar dig) reentrant
{ uchar j,asc,dis[5] ; uint rem=0,div=0; div = disp; for(j=3;j>0;j--) { rem=div%10; div/=10; asc=rem+0x30; dis[j]=asc; } lcdcmd(loc); for(j=4-dig;j<4;j++) { lcddat(dis[j]); } for(j=1;j<10;j++) lcdcmd(0x14);
}