I've got no idea, yet, what's breaking down. The MCU isn't executing code, though. When I use the linear PSU's, several of them it seems it ALWAYS works fine. When I use an SMPS, one of which is a PC PSU, the thing fails to reset, i.e. has NEVER even once reset properly. The only difference is the power source. That's what has me mystified.

I'm not sure how to go about checking to ensure the DS1232 works correctly. It doesn't put out a precisely timed pulse, but simply generates an improved/modified/conditioned reset switch/power-on-reset input.

I'm wondering whether there's a good way to ensure that the 805x receives a reset pulse that makes it work properly. I'm also wondering how one could ensure that a DS1232 is actually producing that pulse. Quite frankly, I doubt it. A proper reset pulse is really not that well defined. I was hoping that one could count the oscillator pulses from the crystal oscillator output, in order to generate a 25-cycle-long pulse that is precisely that long, thereby ensuring what the specifications spell out is met but not exceeded.

I think what's needed is a schmitt-triggered inverter on a "normal" pushbutton-to-GND switch across a capacitor to GND, probably about 100 nF pulled up with 1K-ohm, to start the process, then a counter that waits for, say, 64K counts of the crystal oscillator before generating that reste pulse. I'm just not sure what to do the MCU while it's not yet had that short pulse, so it doesn't get "crazy" in the interim. Holding it in a reset state doesn't seem to work as I'd expect.

I guess I'm going to have to try something else ...

RE