HP48GX RAM card design

[pdo]

(06-12-2017 12:29 PM)pdo Wrote:  Yes, I hoped that the addition of the A17 and A18 switches would allow operation in an SX as well as operation in either slot of a GX but, as I described in the README, something I don't understand is going on there, so now I can't be confident of it working in an SX.

Further testing shows that there is an intermittent problem with one of the two boards I have assembled: it can randomly cause bad card data errors. I need to investigate further, but I suspect a duff solder joint as my soldering is not the best!

However, the other card works fine. It can be used in slot 1, switching between 4 different port 1 configurations via SW17/18's '0' & '1' settings, or in slot 2, mapping the 4 banks to ports 2 to 5 with SW17/18 set to 'A'.

Given this turn of events, I feel more confident that the card should also work in an SX too. I will feel even more confident when I have fixed the problem with the other card!

Paul