timer/counter3 issue

David_Delph · Joined: 23 Oct 2006 Posts: 4 Location: Aberdeen

Hi i'am trying to use timer 3 as a 16bit counter using timer1 external clock (pin RC0/T1OSC/T13CK1). The problem is that it only counts up to 255 before overflowing and resetting back to 0.

The device is a 18F8722.

Does anyone know why this is?

My code sets up timer 3 as follows:

setup_timer_3(T3_EXTERNAL);

set_timer3(0);

encoder_velocity = get_timer3();

If i use timer0 and its associated external clk pin it works but I need to counters running run to seperate sources.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

David_Delph · Joined: 23 Oct 2006 Posts: 4 Location: Aberdeen

No it is declared as an int16.

The code I have works on timer/counter 0 but if I change to using timer/counter 1 it only counts to 255 before overflowing

badtzdizzy · Guest

Hi

I found a solution, you have to clear bit 7 and bit 2 from T1CON register, I did it and I'm getting a 16 bit data.

Regards

eskimobob · Joined: 07 Feb 2009 Posts: 40

Hmmm - that solution did not work for me however I was able to use Timer0 instead and all works properly. The problem with Timer3 seems to be related to reading the two bytes as a 16 bit value - inspecting the RAM, the high byte is always 0.