Hi Joe:
I subscribed and posted to cctech, but found your response in the cctalk
archive. This list is new to me -- do you think I should I subscribe to
cctalk instead of cctech?
>>>I have three or four 9915s and a keyboard... I don't know what the
difference is between an A and a B model... I did make a schematic of my
keyboard but I haven't seen it in a while...
>>>
As I understand it, the 9915A is compatible with the HP-85 (aka HP-85A),
while the 9915B is an 85B. IIRC, the 85B has built-in mass-storage and i/o
roms, and more ramdisk memory than the 85A.
I'd sure appreciate any keyboard info you may run across -- I could program
a little pic to convert a serial keyboard. If this keyboard is used with
other HP machines, other folks might find an adapter handy too.
>>>You need to use the HP composite monitors. IIRC the PN is 82912 and
82913. These are used on the HP 86 and commonly used on the 9000 220 (aka
9920) and are pretty common.
>>>
>>>There were software developement kits available that let you write
programs in assembler and burn them into EPROMs that plugged into a HP-85
type plug-in cartridges (called a Hybrid ROM or something like that) or
directly into the 9915. The EPROMs that are in it are probably Matrix
and/or I/O ROM IIRC. That seems to be standard in the 9915s that I'm aware of.
>>>
Yes, I have a programmable-rom-module and assembler rom (but have not tried
them yet). A buddy of mine has managed to read 85 roms and burn them into
eproms for the prog-rom-module. The original 85 roms seem to be special,
and cannot be simply duplicated.
I opened up a rom, hoping to find a standard package, but found a chip
covered in a blob of epoxy, attached directly to a small board. I opened
the rom drawer card, and found that all six sockets are wired in parallel
(no individual enable lines to each). Then I looked at the signals
connected to the rom card connector (using the serial manual's connector
pinout as a reference). 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. Since there
are no lines to enable a specific rom socket, I think the 85 must poll for
roms using fixed address ranges or something -- this implies that the roms
contain address qualification circuitry of some sort. I'm just
speculating, but it would make the roms very difficult to duplicate, since
this is not a standard address-bus/data-bus (or even a typical multiplexed
addr/data bus).
Thanks for the info Joe,
gil
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Received on Sun Oct 13 2002 - 19:49:22 BST