Mystery instability of 16f628a

[master_olan]

Have you try turning off the analog comparators? if you dont know how just add ADCON1=7 near the top row...

[rsocor01]

Also, add the line

TRISA = 0

[Bruce]

CMCON = 7 will disable the comparators. Also place a small 0.1 or 0.01uF cap between the PIC gnd & vcc pins. Make sure it's as close as possible to the pins.

It's also a good idea to include at least the minimum config options in your code so you're not left with whatever the default unprogrammed config bits are.

I would use at least @ device pic16F628A, intrc_osc_noclkout, wdt_on, mclr_on, lvp_off, protect_off.

If that doesn't take care of it, check your power supply.

[master_olan]

yup..my mistake...its cmcon = 7...

[Davidmarks]

Hi,
Thanks for the suggestions folks. tried them all one by one and got nowhere, then noticed that /MCLR was checked in PicKit 2. Unchecked it and everything worked like a dream ! I then worked backward taking each mod off in turn to see which one had done the trick! Yes, youve guessed it .. the dam thing still worked. I have reintroduced all suggestions again in the hope that this thing shows a tad more reliability, but I'm not holding my breath !

Thanks again
David

[Bruce]

Glad to hear you got it working, but you really do want to include that cap between the gnd & vcc pis. Without it you might have more problems down the road. Some older PIC types could get by without this cap, but most all newer A versions will experience problems without it. Just FYI. It's cheap insurance...

[Davidmarks]

Thanks Bruce. It's back in even as we speak ! Belt, braces and a piece od string as they say !
Cheers

[Archangel]

Hello Davidmarks,
I am curious, are you getting any warnings when you compile? It occurs to me, without the present ability to check MY pbp due to a hard drive failure here at home, What is the default OSC setting in the 16F628A.inc file? Have you opened it and commented it out ? Because if not, your program will use the default osc setting and NOT the one you wrote into your code. So if the default is for using a crystal instead of INTRC_OSC * * * you will in effect have the external crystal ports open to the ether looking for a finger to help start the oscillator by stray capacitance. One more thing, is the " [ " at the beginning of the config statement, in you code or just in your post?