14 Oct
2002
14 Oct
'02
8:55 a.m.
At 08:31 PM 10/13/02 -0700, you wrote:
gil smith <gil(a)vauxelectronics.com> wrote about
HP-8x ROMs:
For the ones of you that aren't aware of it, the handheld HP-75 is a repackaged
HP-85 with CMOS circuitry. They're so similar that if you ordered one of the Assembley
Language packages that they even included some of the HP-85 manuals! The HP-85 and HP-75
were both designed by the Loveland Colorado instrument group. HP adopted the HP-75 over
the STRENUOUS objections of the calculator group then located in Corvallis Oregon. The
HP-75 was the only calculator produced by HP that was designed by anyone outside of the
calculator group.
Joe
The roms have +12V, +6V, and -5V
power. There is an 8-bit bi-directional bus, and four non-overlapping
12V clock signals. There is a "load-memory-address" line, a
"power-on"
line, "read" and "read-control" lines, and even a "write"
line (I don't
know why write is available on a rom).
This all leads me to believe the roms are pretty specialized.
Yup, custom for the HP-8x, and CMOS versions for the HP-75. AFAIK they
aren't used in anything else, although sometimes Corvallis division
custom parts wound up in instruments, like the HP-35 chipset (with
different ROM code) in the 1722A oscilliscope.