pic 18f4520 timer issue

[raman00084]

in my project i am using timer0 (16.3ms overflow, internal oscillator) in that timer0 isr i am incrementing a count variable if count is 10 means led will toggle then i will clear the count to zero so that led will be flashing on and off this works fine. If i switch on and off the power some times that is say for an instance 5 times once the led is not toggling it takes longer time to toggle, the same code i tested with another board that works fine. what could be wrong the pic may be fault only starting problem once its gets started it keeps on working good why this problem comes kindly help

regards
kalyan

 

[zsolt1]

hi,
if the cip where faulty it would not work at all. I think it depends on the oscillator at start up. I'm not shore, but i remember that some mcu-s can start up on internal oscillator before switching to external crystal mode . See datasheet at power on conditions.

 

[wp100]

Hi,

If it works ok on one board but not another it does suggest a hardware fault but without seeing your circuit its hard to say.

However its equally likely you have made some error in the program code or programming method; how are you entering the chips Config details, in the code or separately during programming.
Again show your code so we can see what you are doing.

You could try a simple software delay to flash the led to see if that works ok on the 'suspect' chip