How to make a custom HP-41 rom for the rest of us

[emece67]

(08-05-2016 09:46 AM)damaltor Wrote:  I am actually experimenting with simple microcontrollers to do the job at the moment. as modern micros are fast and cheap, there might be a way to get around fpga/cpld/... stuff, though i cant tell if everything works out like i think it will. i plan on using a small 8bit controller with a high enough clock rate to output the rom data quick enough. this is somewhat tricky, but might work it would also mean that the new rom module has far more processing power than the 41 itself.
in deep sleep modes, recent microcontrollers go down to less-than-microamp currents, so i guess that should not be a huge problem.

I'm on the same quest right now, although I'm using an ARM based controller. In fact I think that a CPLD/FPGA based approach can be better, but I was unable to find a device with enough memory and with in a small enough package to fit inside a 41 module. Add (in case of FPGA) the configuration memory and space gets even tighter.