Hi all, Meindert,
First of all, thanks a lot for keeping the cooperative spirit alive. As far as I'm concerned this is the main goal in our little HP-41'ers community and we all share its benefits.
Some of us spent, literally, hundreds of hours and $$$ to built a "solution", both for our own joy as well as to serve others needs. I'm pretty sure nobody's going to make a "fortune" on this. And side cash will, in most cases, be re-invested on the next project. May some romantic spirit is on the background after all... :-)
Back on the technical aspects of this thread, I haven't found such a "magic" microcontroller (64kFlash 32kSRAM... 5.5v!! and the required small footprint) So I decided to give a try with "standard" devices, Non-Volatile xx256FRAM + new Flash ROM PIC µC.
The required PCB needs, obviously, to be double sided, and the whole layout must be changed too, it must also be manufactured under high quality standards whith very thight tolerances (not a task for one's kitchen or small laboratory, and not cheap either), but it can hopefully fit a standard module housing (I'm quite obsessive about physical space wasting...;-). I'll borrow your contacts for said PCB manufacturing, provided prototyping stage runs OK.
Yes, FRAM is quite expensive, but there's only one chip needed for the job, so I think it would be acceptable. Anyhow, I haven't get the FRAM samples to start prototyping, but I can make a first attempt with standard SRAM as FRAM is pin to pin compatible (timing is not though.)
For now I'm still preparing my Clonix PCB's and populating them with the required components, they'll be for sale at the pace module shells reach my hands. (Not a high rate for now... I must say)
Kind regards.
Diego.