3 Jul
2000
3 Jul
'00
2:20 a.m.
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