Counter overflow?

[tsen0017]

Hi,

I'm new to this and have some basic questions. Here is a portion of my code:

void main() {
setup_comparator(NC_NC);
setup_adc_ports(NO_ANALOGS);
port_a_pullups(8);
for(CYCLES=108000;CYCLES!=0;--CYCLES) {
send_pulses();
output_low(PIN_A5);
delay_ms(60);
}
output_low(PIN_A2);
output_low(PIN_A5);
delay_ms(3);

I use CYCLES as a counter to control the microcontroller (When the counter expires, the microcontroller outputs LOW on PIN_A2 and PIN_A5). The microcontroller does NOT output LOW WHEN the counter expires if CYCLES is set to 108000 ( instead it happened about two hours AFTER the counter expires) ; it works correctly if CYCLES is a smaller number (I tried 450 and 900). I use int32 for the variable CYCLES.

Could anyone point out why this is causing me problems? Maybe overflow?? Any suggestions? I'm using PIC12F675.

Your help is highly appreciated.


John

[PCM programmer]

1. Post a complete test program that shows the problem. In other words,
add the #include, #fuses, and #use delay() statements to the program.
Also add the variable declarations. Show the closing brace of main().
Test the program, verify that it fails, and post it.

2. Post your compiler version.

3. Describe any external circuits that you have connected to the PIC.

[ckielstra]

[tsen0017]

Thanks a lot for your reply. I have posted the code below.

Basic I expect the microcontroller to output LOW (and stops sending pulses) on both A2 and A5 after ~108000 * (24*1ms + 60ms) = 2.5 hrs. Output of maybe 10 times I tried, it only worked 3 times (it stopped sendig pulses after 2.5 hrs, which is expected). For other 7 times, it continued sending pulses (after the 2.5 hrs) for quite a while (~ 2 hrs, but this extra time varies).

Besides VDD pin and GND pin, MCRL is connected to VDD(5V) through a 47K resistor. A2 and A5 are not connected to anything.

I really appreciate your help.


John

[tsen0017]

Sorry I forgot to post my compilier version. It's:

CCS PCM C Compiler, Version 4.049, 40044

Thanks,

John

[Ttelmah]

How is the supply generated?. What capacitance have you got between Vss and Vdd (amount, and where placed)?.
I'd suspect something is 'spiking' the chip, and the code is restarting. Hence the variable times involved.

Best Wishes