Hello Asok Sankar Rudra,

Below is the clock.c for SDCC. I have also compiled this
same file with RIDE (Raisonnance Inc) and was able to
get the size decrased by about 300 bytes. Only one line
was needed to be changed (#include <at89x51.h>). The
debugger in RIDE allows you to troubleshoot this
program. This is a demo program with out the trouble
Keil puts you thru.

Good luck,

Charles Bannister

   CLOCK V1.0
   89C2051 @11.0592MHz + 4-digit 7-SEG led + 4-key switch
   Simple Digital Clock demostrates scanning LED and key switch.
   The clock has 1-bit output port P3.7 for driving AC load through MOC3040+triac.
   
   The source program was modified for sdcc for 8051
   January 27, 2004

           *    ****       ****    ****
           *   *    *  *  *    *  *    *
           *   *    *     *    *  *    *
           *    ****      *    *  *    *
           *   *    *     *    *  *    *
           *   *    *  *  *    *  *    *
           *    ****       ****    ****

              set   set  time    manual
             HOUR   MIN  ON/OFF  ON/OFF


  Copyright(C) 2004 WICHIT SIRICHOTE, kswichit@kmitl.ac.th

  This program is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the
  Free Software Foundation; either version 2, or (at your option) any
  later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

*/

#include <at89x51.h> 
#include <stdio.h>
 
unsigned  char sec100,sec,sec5,min,hour,flag1,command,temp,opto;
unsigned char i,digit,buffer[4],onHour1,onMin1,offHour1,offMin1;
char cputick,key,delay,count1;

char code convert[10] = {0x3F,0x0c,0x76,0x5e,0x4d,0x5b,0x7b,0x0e,0x7f,0x5f};


void pause(int); 
void scanLED();
void manualOnOff();
void savetimeOnOff1(); 
void setmin();
void sethour();
void showOnce();
void savetimeOff1();

void time();
void timeToBuffer();
void blink();
void offmsd();
void keyexe();
void keydelay();
void comparetime();

void timer_isr (void)  interrupt 1  using 1  {
	TH0 |= 0xdc;  // reload timer 0 with 0DC00H
	cputick++;
	time();       // update realtime clock
         
}

void main()
{
  EA = 1;
  ET0 = 1;  // or IE |= 0x82;   /* set bit EA and Timer0 enable */ 
  TMOD |= 0x01; /* timer 0 run 16 bit counter */
  TR0 = 1; //or TCON |= 0x10; /* run timer 0 */
  opto = 0xff;
  cputick = 0;
//  hour = 18;
  hour = 12;
  min = 0;
  sec = 0;
  key = -1;
  flag1 = 0;
  onHour1 = 18;   /* 18:30 turn lamp on */
  onMin1 = 01;
  offHour1 = 18;   /* 21:30 turn off */
  offMin1 = 02;
  count1 = 0;
  buffer[0] = 0x40;
  buffer[1] = 0x40;
  buffer[2] = 0x40;
  buffer[3] = 0x40;

  while(1)
  {
    while ( cputick < 1)
    scanLED();

    cputick = 0;

/*------------- the following tasks execute every 10ms ------*/

   // time();
    timeToBuffer();
    blink();
    offmsd();
    keyexe();
    keydelay();
    comparetime();

/*-----------------------------------------------------------*/
   }
}

/* ****************** change constant below for another X-tal ********/
void time ()
/* update real-time clock  */
{
   sec100++;
   if (sec100 >= 100)       /* 100 * 10 ms = 1 s */
   {sec100 = 0;
    flag1 |= 0x05;   /* set bit 0, bit 2 */
    temp = 50;
    sec++;
    if (sec >= 60)
    {sec = 0;
     flag1 |= 0x02; /* set bit 1 */
     min++;
     if (min >= 60)
     {min = 0;
     hour++;
//     if (hour >= 24)
//     {hour = 0;
	if (hour >= 12) 
	{hour = 0;

    }
  }
 }
}
}

void scanLED() /* scan 4-digit LED and 4-key switch, if key pressed key = 0-3
else key = -1 */

{
    int i;
    digit = 0x08;
    key = -1;
    for( i = 0; i < 4; i++)  /* 4-DIGIT scanning */
    {
        P3 = ~digit & opto;  /* send complement[digit] */
        P1 = ~buffer[i];  /* send complement[segment] */
        pause(5);         /* delay a while */
        P1 = 0xff;        /* off LED */
        if ((P3 & 0x10) == 0) /* if key pressed P3.4 became low */
           key = i;       /* save key position to key variable */
        digit>>=1;        /* next digit */
    }
}


void timeToBuffer()
{
    buffer[0] = convert[min%10];
    buffer[1] = convert[min/10];
    buffer[2] = convert[hour%10];
    buffer[3] = convert[hour/10];

}

void blink()
{
    if((flag1 & 0x04) != 0) /* check bit 2 if set decrement temp until zero */
     {temp--;
        if (temp != 0)
                {
                buffer[1] |= 0x80;
                buffer[2] |= 0x80;
                }
                else( flag1 &= ~0x04);
      }
}


void keyexe()
{
    if (key != -1)
    {
        if ((flag1 & 0x80) == 0)  /* within 0.5 sec after 1st press
                                    the following execution is not allowed */
            {
                flag1 |= 0x80;
                delay = 50;

      switch(key){
        case (0): /* key position 0 */
        manualOnOff();    /* service key 0 */
        break;
        case (1): /* key position 1 */
        savetimeOnOff1();  /* service key 1 */
        break;
        case (2): /* key position 2 */
        setmin(); /* service key 2 */
        break;
        case (3): /* key position 3 */
        sethour();
                  }
                }

    }
}

void sethour()
{
    hour++;
    if ( hour== 24)
    hour = 0;

}

void setmin()
{
    min++;
    sec = 0;
    if( min == 60 )
    min = 0;
}

void savetimeOnOff1()

{
    count1++;
    if (count1 == 1)
    {
    onHour1 = hour;
    onMin1 = min;
    buffer[0] = 0x00;
    buffer[1] = 0x68;
    buffer[2] = 0x78;
    buffer[3] = 0x71;
    showOnce();
    }
    else
    {
        count1 = 0;
        savetimeOff1();
    }
}

void savetimeOff1()

{
    offHour1 = hour;
    offMin1 = min;
    buffer[0] = 0x63;
    buffer[1] = 0x63;
    buffer[2] = 0x78;
    buffer[3] = 0x71;
    showOnce();
}

void manualOnOff()

{
    opto= ~opto | 0x7f;  /* complement bit 7 which in turn activates P3.7 */
    if ((opto & 0x80) == 0)
    {
        buffer[0] = 0;
        buffer[1] = 0;
        buffer[2] = 0x68;
        buffer[3] = 0x78;
        showOnce();
    }
    else
    {
        buffer[0] = 0;
        buffer[1] = 0x63;
        buffer[2] = 0x63;
        buffer[3] = 0x78;
        showOnce();
    }
}

void showOnce()
{
    int i;
    for(i=0;i<2000;i++)
    scanLED();
}
void keydelay()
{
    if ((flag1 & 0x80) !=0)
        {
            delay--;
        if(delay == 0)
            flag1 &= ~0x80;
        }
}

void comparetime()
{
    if((flag1 & 0x01) != 0 )
    {
        flag1 &= ~0x01;
    if(hour == onHour1 && min == onMin1)
            opto = 0x7f; /* clear P3.7 turning opto on   */
    if(hour == offHour1 && min == offMin1)
            opto = 0xff; /* set bit P3.7 turning opto off */
    }
}

void offmsd()

{
    if (buffer[3] == 0x3f)    /* if msd = '0' then put blank unstead */
       buffer[3] = 0x00;
}


void pause(int j)
{
   int i;
   for (i = 0; i < j; i++)
   ;
}