HP 85 stuff

From: Joe <rigdonj_at_intellistar.net>
Date: Mon Jul 3 09:20:16 2000

At 10:46 AM 7/2/00 -0700, Jim wrote:
>At 08:03 PM 7/2/00 +0930, Geoff Roberts wrote:
>
>
>The uP itself fits in a 28 pin DIP, with a single 8b data/address bus. All
>the peripherals that connect to this bus know the protocol so that many
>times the address doesn't need to be transmitted at all. For example,
>everyone on the bus basically keeps a copy of the PC, so as long as
>instructions are fetched sequentially, no address is sent an the ROMS
>and RAMS just keep incrementing their copy of the PC. Things like
>jump instructions cause the uP to send the address out (in two cycles,
>of course, it is a 16b address).
>
>I believe that the HP 75 uses this same processor, as of course the
>HP 86 and HP 87 do too.

    Yes, the HP 75 uses a CMOS version of the HP 85 CPU. In fact, when you
bought the assembly langauge programming material for the HP75 from HP they
included a copy of the assembly language book for the HP 85.

>
>This and a lot more is documented in the assembler ROM. It has a wealth
>of information. Enough, in fact, that I've been toying with writing an
>emulator
>for it, but of all the defunct old computers, HP is one of the few that is
>still
>in business and would probably seriously care if someone ripped their ROMs
>for an emulator. If somebody thinks HP might not care, then I might consider
>writing the emulator.

    I'd like to see an emulator for it. I doubt HP would care, they've been
good about giving their permission for people to copy manuals and what not.
I know several people that have gotten HPs permission to copy stuff. If
you're serious about writing the emulator I can check with them and find
out who to talk toat HP about getting permission to copy the ROMs.

     Joe
Received on Mon Jul 03 2000 - 09:20:16 BST