Timer1 prescaler not work, PIC18F24J11

[Eduardo__]

I don't know why prescaler configuration doesn't affect Timer1 counting frequency. Despite of prescaler configuration, it seems like T1_DIV_BY_1.

I've tried to configure it manually, but without success.
Actually (even when T1_DIV_BY_8) the Timer1 overflow is occurring each two seconds, but it should be 16seconds). I've tried other prescaler values, but without success.

See the code:

[Ttelmah]

To use an external crystal on T1, you need:
T1_ENABLE_T1OSC

Without this, it'll assume you are feeding a clock in on the input pin. I'm surprised it gives anything.

setup_timer_1(T1_EXTERNAL | T1_ENABLE_T1OSC | T1_DIV_BY_8);

However I'd have expected your manual settings to work. Do a text search on the code and 'make sure' nothing else is changing timer1. It sounds as if something else is changing the value.

Compiler version?.

Best Wishes

[Eduardo__]

Dear Ttelmah,

You´re right again, I forgot timer1 Enable bit(T1_ENABLE_T1OSC).


I´m using compiler version 4.124.
Function setup_rtc(RTC_ENABLE,0) was changing Timer1 configuration.

Can this function change T1CON or could it be just a bug?

Thanks a lot!
_________________
Eduardo Guilherme Brandt

[jeremiah]

The RTC on that chip can use the T1 external clock input. If you check the data sheet for the PIC (section 17.2.2.1) you'll see that the RTC has to enable bit 3 of T1CON to work, so setup_rtc() probably does affect the register.

[Eduardo__]

Thanks Jeremiah.
_________________
Eduardo Guilherme Brandt