How to test memory in an HP48 RAM card

[mfleming]

Bob,

When first working on my own card, I was surprised to find that power was removed when the calculator is shut off. I should have known better though, hot-plugging wasn't the fashion back then. The capacitor across the device power pins does keep memory alive for a short time after power and battery are removed thanks to a 1 uA standby current draw.

I'm limited to an HP 48SX at the moment, so the PINIT command is not available. There is a noticeable pause when purging a variable for the first time which leads me to suspect some sort of memory test or "formatting" is going on, but I've never read about any details.

I'm probably concerned over nothing, but I may try the brute force approach you mention. Having the address space wrap around a given address bit would certainly cause corruption at some point!

~Mark