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teenix · 02-09-2017, 05:46 AM

Hi all,

I have uploaded a simulator for the HP-91 printing desktop scientific calculator to teenix.org

I did not have access to the microcode for this calculator, so I looked through the various classic models and the HP-55 had the closest match for the functions required for the HP-91.

There were a few extra functions needed for the HP-91 so these were added by the Windows program tapping into the HP-55 microcode and getting it to execute the required mathematics. Therefore, the results should be exactly like the HP-91 would have produced.

The HP-55 code only had 1 ROM location modified due to the Woodstock style "Error" displayed on the HP-91, and of course, not all of it is used.

The simulation proved to be a difficult task as the Windows program has to monitor the code flow of the HP-55 so it can intercept it and extract register and key code data for the print routines.

It all seems to work as per the operating manual.

cheers

Tony