--- Quote Start ---
The reset controller looks like the culprit to me, or the 3.3V rail (which you didn't measure above). Just to isolate the problem, can you lift a lead on the reset controller so it can't pull nCONFIG low, then configure the part via JTAG in the failing temperature range?
One other thing to note is that you've got the MSEL pins set for the fast POR delay. According to the CIV handbook: "The fast POR time option has stricter power-up requirements when compared with the standard POR time option." This could be something to look at, but it would not cause the reset controller to keep pulling nCONFIG low. That still points to the reset controller.
--- Quote End ---
Yeah, that's what we have found also. It turns out the tolerance on 3.3V, the tolerance of the reset controller, and the hysteresis of the controller combined to make it marginal at -40C. We have replaced the reset controller with a lower threshold version and all is good.
Thanks everyone for time and suggestions.
Honored Contributor
