AVR-Chat

At 07:19 AM 7/25/2005, koorosh wrote:
>hi again
>
>but how can i use counter for 1000,you know ,i could get only 1
>milisecond from 8 bit counter.and how can i make it with 16 bit
>counter?
>can you write the codes? what would you do if you have to make 1
>second for a digital clock?

I use a 1mS interrupt to count out through weeks in one application.

Set an intermediate counter to increment once a millisecond, and then 
every hundred mS, increment at tenths of seconds counter.
Every time that hits 10, increment the seconds counter, and so on.
When you increment the next counter, zero this one:

In this example, I had a timer interrupt that happened every 5mS

         ;We get here every 5mS

Int_HMS:
         lds             TEMP,HMS                ;Hundred millisec
         dec             TEMP                    ;
         sts             HMS,TEMP                ;
         and             TEMP,TEMP               ;Return if not zero
         breq    Int_HMS_Done                    ;
         ret
Int_HMS_Done:
         ldi             TEMP,20         ;Reload the 100mS (20*5 = 100) counter
         sts             HMS,TEMP                ;

         ;We get here, every 1/10th second

         lds             TEMP,Tenths             ;
         dec             TEMP                    ;
         sts             Tenths,TEMP             ;
         and             TEMP,TEMP               ;
         breq            Int_HMS_Done            ;
         ret
Int_Secs_Done:
         ldi             TEMP,10         ;
         sts             Tenths,TEMP             ;

         lds             TEMP,Seconds            ;
         ;And so on...