The HPC was a fine micro in its day - I believe it was one of the fastest microcontrollers available at the time (15 years ago?). It's a
16-bit accumulator-based CISC cpu, with a reasonable range of addressing modes. We used to have an emulator for it, but it's unfortunately broken. It was an impressive system - a main board around 50cm by 50cm, with a "daughter" board at about 30cm by 50cm. The assembler was, as far as I can remember, free (or at least very low cost), while the C compiler from National Semiconductor cost extra. It's been about 10 years since I've written a new program on the HPC, but the last modification I made to a HPC program was a couple of months ago.Talk to your National Semiconductor representatives about tools and documentation. If they can't give you the tools, but can authorize a free copy, then I can send you a zip of the assembler and linker (and C compiler, if they authorize that too). That might be easier to deal with than the originals, which I believe came on 5 1/4" floppies. The documentation would be harder - I think I only have it in dead tree format.
As long as you don't have to debug anything (which you might avoid, if you are only modifying a working system), then the HPC is fine to work with in assembler, or even its (slightly limited and very old fashioned) C compiler. It's certainly much more programmer friendly than many
8-bit micros.Good luck!
David
(If you want to contact me directly, I'm sure you can figure out my email address.)