How to make a 1 minute counter using TMR1 in PIC16F628A?

dear all.

how to have a counter that will count for 1 minute...by using TMR1 in pic16f628a
i reer to use an interrupt

previously i use delay a minute from piclist code generator.

here the code fo 1 minute delay


how do i modify thsi code so that it can be use for TMR1

thanks in advance

1 minute count

Locate the register of the TMR1, better yet use C language, will save lots of trouble.

Re: 1 minute count

Hi !

Using TMR1 and the PIC main oscillator at 4MHz is impossible to have 60s counting, because the maximum prescaler is 8 (clock division). At 4MHz and prescaler = 8, TMR1 will overflow every 524288 us or aproximattely every 0,5s, as follows:

65536 x 1/fosc/4 x 8 prescaler

65536 x 1us x 8 = 524288 us

If you use a 32768Hz in the TMR1 external oscillator, you can obtain 16 s counting (steps of 244.141 us)

You can configure TMR1 (with 32768 Hz xtal) to overflow every 15 s, make the interrupt and increment a variable. When such variable reaches 4, you have your 60 s timing (and clear the variable after this).

Another idea is using a low frequency clock feeding the TMR1 input, lets say 1000Hz. This way you get 60 s when TMR1 reachs 60000.

Re: 1 minute count

rkodaira said:

If you use a 32768Hz in the TMR1 external oscillator, you can obtain 16 s counting (steps of 244.141 us)

.

Click to expand...

I have a question....
what will be the value of the prescaler ???
where we have 15s= y*(4/fosc)*256
if fosc = 32768Hz....this will give y=480!!!!

Re: 1 minute count

Salam,

If u want an accurate delay for any application do as rkodaira said, but if u intend to make a clock use 4MHz Xtal and /8 prescaler then u can subtract the error every while.

Hope that this this is what u r asking for and that i've helped u