8 Pin PICs - How to program ?

[ac34856]

I was just thinking I would like to add an additional watchdog but in hardware for a *very* safety critical system, an ideal candidate is an
8 pin PIC but I've never programmed them before. It would then only need to monitor the status LED which should blink every 100mS and if for some unspecified reason the main PIC hangs and the WDT doesnt sort it I'm covered.

I have an ICD2 clone (no ZIF socket) and an olimex PICstart clone with a
ZIF.

Am I right in thinking the 8 pin pics need to be programmed via the ZIF on the PICStart or is there something else I need to consider ?

[PCM programmer]

For a 12F675, you can program it in a PicStart-Plus, or you can use
an ICD2 to program it in a board with ICSP.

[SherpaDoug]

What is the chance of the 8 pin PIC failing and causing the system to fail? Adding more parts or more software doesn't always improve reliability.
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[dyeatman]

It seems to me the cheapest and easiest solution would be the Maxim MAX16056-MAX16059 watchdog chip at less than $2.50 it is a quick and easy fix for your problem.
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[Yarnus]

I think your best option (other than a dedicated watchdog IC) is using 'missing pulse detector'.

It's a relatively simple circuit and much more reliable than a MCU.

You can find several schematics if you google 'missing pulse detector 555'.

[Guest]

I used the 74123 on several DEC LSI-11 systems in steel mills in Ontario as a 'watchdog'...even made them to fit the OAC-5 style SSR racks.
man, that was 30 years ago......do they still make 74123s????

[Mike Walne]

Yes I agree. Work on the KISS principal.

Guest quotes