PIC failure ?

Gon · Guest

Hello,

i wanted to know if it was possible for a PIC (a 18F my case) to fail but not its interrupts ?

I mean, if i have a programm on this PIC, and its interrupts handle a LED, would the PIC will still make blink the LED, and doesn't mind that the PIC failed or not ?

I putted some watchdog that sould reset the whole thing, if it fails, but it seems that sometimes, the led is still blinking but the PIC is not 'working' anymore...

Another question :
Is it possible that a PIC fails because of another component, i mean, if on one of its pin, the PIC receive a high level or a low level, is it possible that this component could make the PIC fail ?

Any explanations would be welcome.

Please let me know.

Many thanks.

Best regards.

iso9001 · Joined: 02 Dec 2003 Posts: 262

I have no idea what you are talking about. Try being a little more specific. What is failing ?

If the LED is blinking you pic is running. (Assuming its not one of those dumb blinking leds)

nm: just read watchdog as PCM pointed out

Humberto · Posted: Tue Feb 28, 2006 11:06 am

To assume that a microcontroller can fail is not a good way to begin. Respecting the good
arts of the hardware design + a simple and safe code is the best combination for a
reliable system.

I do not know a single case where one can suppose that a microcontroller works bad, in
the 99,9999% of the cases always is an external cause that produces it, assuming as
external cause a wrong code or wrong hardware or both.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Gon · Guest

Thank you for the answers.

It is just a small part of my programm to understand what was wrong because it seems to be a bug that comes up once without any reason.
And the only thing i could visualize is the LED, so i try to understand what was wrong in all the hardware or software.

Is it possible that a pic that fails just when a led is on and then, let it switched on although there is a watchdog ?

Is it possible to have a watchdog that fails as well ?

In my case, the PIC is not doing what it should do anymore. But when it failed the led was on and it didn't reset with the watchdog, i don't know why.
I assume that if the pic failed, after the watchdog duration, it should have reset itself...

rberek · Joined: 10 Jan 2005 Posts: 207 Location: Ottawa, Canada

Anything is possible. Microcontrollers can be complex beasts and the failure modes are many. It could fail in thousands of different ways. But is it likely? No. The things that you just did (i.e. firmware, hardware, board layout, construction technique) are most likely the cause.

These are rather open ended questions you are asking, so an exact explanation is NOT possible. Without much in the way of extra detail from you, we can only shrug our shoulders and say "maybe". However, if we had all said, "its the PIC for sure!", what would you do?

You'd have to do this - replace the PIC. If you put in a new device, and the behaviour has not changed, your firmware or the other hardware are at fault. This is where your debuging skills will have to save the day for you.

Debugging firmware will involve code inspection, simulation (in MPLAB or other) or in circuit debugging.

If the hardware is at fault, then you may also have to simulate it, if you have the resources, or get the oscilloscope/logic analyzer out and isolate the offending part.

All the best
_________________
The difference between genius and stupidity is that genius has its limits...

asmallri · Joined: 12 Aug 2004 Posts: 1634 Location: Perth, Australia