PIC12f629 Timer1 Interrupt issue

[shahram642005]

hi,
can anybody help me how to make timer1 interrupt work properly in every PIC12f629. I set a timer value to a pic mcu that gives a 400us interrupt, but when i change the micro the time interval changes. how can i have a precise constant time interval in every PIC12f629 that i use? By the way, I use internal clock source.
best regards

 

[betwixt]

PIC12F629 devices have a calibration value to ensure the internal oscillator frequency is correct. Are you using it? Also make sure that you do not erase it when you reprogram the IC, the value is stored in a "movlw" during manufacture and it's quite easy to wipe it. You should find it in the final memory location. Full details are in the data sheet.

Brian.

 

[shahram642005]

I know about the calibration data and I keep it unchanged. but the problem is sth else.

 

[wp100]

Hi,

how can i have a precise constant time interval

Depends on your definition of "precise" , what kind of accuracy are you expecting, 400us; plus or minus how many us ?

How efficient is your program code ?

Have you tried using a crystal which should be a lot more stable; also try using a much higher frequency than the internal 4 mhz so any error is reduced.

Made any consideration for temperature variations ?