HP-75 Re: HP 9915A (industrial version of HP 85A)

From: Joe <rigdonj_at_cfl.rr.com>
Date: Mon Oct 14 08:55:22 2002

At 08:31 PM 10/13/02 -0700, you wrote:
>gil smith <gil_at_vauxelectronics.com> wrote about HP-8x ROMs:
>> 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.

   

    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
Received on Mon Oct 14 2002 - 08:55:22 BST