hey kerry i used your code and found some weird results
here i used both (ur code for delay and delay_ms(10)) n the result was 10ms
delay loop gave a delay of approx. 6 seconds while delay_ms gave a delay of
2 seconds and after that i changed the clock freq in code to 20MHz(using
same 4MHz crystal) and here both delays gave a delay of 10seconds.
i think the crystal oscillator is definitely not giving 4MHz but why delay
loop and delay function are not giving same results?

code used=20
#include <16F877A.h>
#use delay(clock=3D20000000)
void main()

{
int16 i,j;
while(1)
{
output_D(255);
   for(i=3D0;i<10;i++)                                //gave a delay 6sec
   {
      for(j=3D0;j<100;j++)                      =20
      {
         #asm
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
      #endasm
      }
};
output_D(0);
delay_ms(10);                 // gave a delay of 2sec.
}
}



Kerry Wentworth wrote:
>=20
> My somewhat outdated CCS compiler does delays using NOPs in a loop, not=20
> a timer.  Also, the 877 has no internal oscillators.
>=20
> Since you don't enable interrupts (and they default to 'off'), it seems=20
> to me it can only be 2 things:
>=20
> 1)  The debugger is using a LOT of time (seems unlikely)
>=20
> 2)  The oscillator is not really running at 4MHz.
>=20
> Try running without the debugger (config=3D0F09), because that's easy.
> If that doesn't do it, write your own delay
>=20
> ms_delay(int d)  // Only works with 4MHz clock!!!
> {
>     for(i=3D0;i<d;i++)
>     {
>        for(j=3D0;j<100;j++)
>        {
>           #asm
>              nop
>              nop
>              nop
>              nop
>              nop
>              nop
>              nop
>              nop
>              nop
>              nop
>        #endasm
>        }
>     }
> }
>=20
> If that gives you the correct delay, the problem is the delay_ms()=20
> routine, otherwise, it is the clock frequency.
>=20
> Kerry
>=20
> geetansh arora wrote:
>> sorry i missed some details which might be important in solving this
>> problem.
>>
>> I started with my first project but it didn't worked so i decided to go
>> back
>> and blink leds,now the problem is when the delay between on off  was set
>> 10ms the leds took 2.3sec(used a stopwatch n delay was approx. 2.3sec).
>> At first delay was set to 500ms but it took too much time to blink so
>> delay
>> was set to 10ms.
>> CCS compiler demo version was used for compiling , 4MHz crystal
>> oscillator
>> was used with 22pF capacitors and configuration bits 2F09 were entered i=
n
>> PICKIT 2 v2.61 (not used in the code)
>>
>> #include <16F877A.h>
>> #use delay(clock=3D4000000)
>> void main()
>> {
>> while(1)
>> {
>> output_D(255);
>> delay_ms(10);
>> output_D(0);
>> delay_ms(10);
>> }
>> }
>> please solve my problem guys.
>> thank you and sorry again for missing the details in previous post.
>>  =20
>=20
> --=20
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>=20
>=20

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