Here’s Jeff Parsons’ very nice microcode-level emulator of TI’s affordable programmable calculator, the TI-57:
TI-57 with Original ROM and Diagnostics
There’s also a version with a revised ROM and the backstory for that…
And here’s his blog about his own TI-57 and what he did next:
It may be the first open-source bit-identical emulation of this calculator - there’s a nearby page about the ROM and about a previous closed-source
emulator:
Texas Instruments TI-57 ROMs
One possible source of ROM data is from TI’s patents, but they seem to differ in small ways from the ROM embedded in the closed-source emulator. Another source is from photographs of the chip used in the calculator - and Sean Riddle decoded the ROM from photos taken by John McMaster…
… and that’s the personal connection - John’s photos are of the chip I took out of my own TI-57!
My first programmable calculator
See also Ten thousand primes on a programmable calculator
(via Claus Buchholz’ TI-57 Memory Map as linked in the RCL-57 thread on HPMuseum forums which lays out how to make good use of 160 bytes of RAM.)