71B vs 75D

[rprosperi]

(04-14-2021 04:50 PM)hth Wrote:  This was interesting. I had a look at the Capricorn CPU and it seems like a quite capable and interesting 8-bit ISA.

Is it possible to write assembly language programs for the HP-75 and just bypass the built in BASIC? What about documentation, if I want to access HP-IL at assembly level, is it around, both hardware and system listings?

You can write LEX files in assembler, but I believe there is not any way to create a complete binary program file, the 75C has no native support for this type (which is why the 71B, which came a year later, added this capability). So you can write a shell program in BASIC, but use new KEYWORDS from LEX files to do the heavy lifting.

There is no IDS for the 75C, however the 75C OS listings were released under NOMAS, and are included in the MoHPC document set, which you likely have.

Also, the I/O ROM listings are there as well, and this is loaded with HP-IL stuff. In fact the native 75C can only handle simple user level commands (COPY file, PRINT, CAT, etc.) on its own, the I/O ROM is needed to do anything meaningful. There is also a small LEX file RIOWIO (Read I/O, Write I/O) available, which I believe is also floating around somewhere in source form. The I/O ROM may provide everything you need, it greatly extends the 75's HP-IL capabilities.

If you're interested in getting into the 75C/75D, I suggest you join this news group, and look at the quite extensive set of documentation:

https://groups.io/g/hp75