16F88 internal clock configuration

[mister_e]

o.k now it seems more a hardware problem than a software problem. be sure your supply line is neat an un-noisy. 10uF tantalum+0.1uF must be place close to your PIC... AS close as you can.

AND be sure your MCLR pin is tie to VCC via resistor.

Enable power-up timer can be great. Also as Melanie previously said it can be interesting to test the 'oscillator frequency is stable bit' before proceed to any of your initialisation process.

look at the a/d register setting(ADCON and others)... i'm sure that they're different from the PIC you used before.

[Tom Gonser]

The hardware is pretty skimpy.. I have the F88 a 5.1v supply, and a resistor from MCLR to power. I have only power and ground supplied, and then serial lines out from the appropriate port pins. No caps no nothing.

Whats odd is that with small program.. like only a portion of the one I am porting over, it works. It wakes up, it does its routine, then it starts doing a simple read from data input, put data into array, and read data from array out to the three serial outputs. This works fine.

Whats odd is when I put my WHOLE program in place, it chokes.. It periodically shows the data, but when it does the math is always wrong, and it looks to be resetting as I see the initialize routine results now and then.

I don't know about ADCON as I am only doing serial data in on Port B1, and serial data out on B2 and also A0,A1. I am setting the serial data out on A1 to 4800b by using SERIN2, and the rest is 9600b. - But again, this seems to work fine with a smaller program...

Must be some timing setting beyond what I've had to set before.

TG

[mister_e]

so there's no analog to digital conversion on a.0 and a.1 ???

you must disable those analog pins to make them digital.. at least

ANSEL=3 'set a.0 and a.1 as digital input

and capacitor should be consider.

[Tom Gonser]

Set the .. ANSEL=3 'set a.0 and a.1 as digital input, thx. Probably a good idea, but did not have any impact.

Oddly as I test, I find that my setting for OSCAL 8 mhz or OSCAL 4 Mhz does not have any impact on the system..

I have tried:

OSCCON=%01101000 ' 4 mhz
DEFINE OSC 4

----

and in another test...

DEFINE OSC 8
OSCCON=%01111000 '8 Mhz


Something must not be getting written somewhere. I'd expect that these settings would have a big impact on overall system operation.

Is there some prescaler setting that I am missing?

tg

[mister_e]

prescaller have nothing to do with your code if you're not using TIMERs. Can you post your code here or it's a 'military secret'

[Tom Gonser]

This program reads a data sentence sent at 9600b 8,1.n. The sentence has two start bytes, then 34 data bytes. It works on the 16F876A on the test board from Microchip, but the plain old F88 on my breadboard is acting strange as the thread indicates..

TG

[mister_e]

reason is simple... you run out of memory...

PIC16F876 : 8K
PIC16F88: 4K
YourCode :4287 words

so you can for sure shrink it using internal or external EEPROM instead of arrays and few other things. It has to fit in a 4k memory space