Peculiar PIC 16F877 behaviour

[arunb]

Hi,

We recently deployed a datalogger unit (meant for industrial use) in a high temperature zone, (temp. range- 65- 70 degC).

At first the unit worked well , later when the temperature in the plant rose to 65degC + , the PIC started to misbehave, I noticed that the program counter was working normally and so were the interupts ( RS 232 , Timer ) .

But I was unable to write to the external EEPROM ( 24LC0256) apart from this problem the PIC was quite normal.

I also noticed that the same PIC worked quite well at normal temperatures

My question is does the PIC stop working altogether at elevated tempertures or do some parts stop functioning ??

Also why did the PIC start working again at lower temperatures ??

cheers
arun

[PCM programmer]

Were you running the Commercial temperature range chip
or the Industrial range ? The Commercial tops out at 70
degrees C, but the Industrial goes up to 85 degrees C.
What oscillator speed were you running at ?

[Guest]

Maybe the external EEPROM was flaking out if the other PIC functions were working....