We have a product that incorporates an AT32UC31512C. Recently we have started to get some reports from the field of devices where the software appears to be rebooting spontaneously.
In my search for the cause of this unpleasant behaviour, I got probing the RESET line to the micro. The RESET line is driven by a Microchip TCM809T reset controller through a 10K series resistor. That resistor is there to allow the programmer to drive the RESET line during production programming.
I discovered that just touching the RESET line with a scope or multimeter probe frequently causes the micro to reset. I connected a scope probe and then touched with the multimeter probe to see what happens. There is a brief glitch of much less than 1us, presumably due to the capacitance of the probe.
According to the Atmel specs, the RESET input is glitch filtered: http://atmel.force.com/support/a... Any pulse shorter than about 8.5us should be ignored.
I don't think I have ever encountered a micro that would reset just because I touched the RESET line with a probe. Has anyone else seen anything like this? Any idea why this might be happening? Something else I should be thinking about?
In the fuse settings, I have disabled the 3.3V BOD, since the errata explain it doesn't work. Just to test I also disabled the 1.8V BOD, but that made no difference.
Thanks for any insights.