3 May
2004
3 May
'04
3:09 p.m.
There are unless you got the optional Hi-Performace
bit-slice CPU. One
I think I may well have that. I know little
of the history of my 9845, other than when I got it it came
with 2 8" drives, a few 16 bit parallel interfaces, 3 HPIB interfaces
(!) a real time clock at least one RS232 interface and the rather
hard-to-find 9878 expansion chassis.
hard to find? Sheesh I find them all over. nearly every 9825 that I find comes with one. I just passed one up in a scrap yard a
couple of weeks ago.
Also passed up a couple of the RTC modules. The RTC modules with the IO
cable are cool. You can interface them to external devices and trigger the
All the clocks have the connector and logic for the external interface,
it's just a cable you have to add.
devices or use the device to trigger events in the
9845.
YEs..
That clock is one strange design. When the machine is powered up, the
clock is done in software on the HP microcontroller inside. But there's
also a digital watch chip (!) which is battery backed and used to keep
the time when the machine is powered down.
The interface to the watch chip is what you might expect. a couple of
'buttons' for things like selecting the time/date, setting the clock,
etc, digit strobes (outputs from the watch chip) and the 7-segment
outputs (one of which isn't used, since the microcontroller can identify
the digit without it). I think there's also an annunciator output, which
means there are only 3 digit strobes (the most significant digit is
either blank or 1, both for time and US-style date, so you just need a
single line for it, rather than a complete digit.) You can actually
attach a 7 segment display to traces on the board and get it to display
the time when the clock module is starting up.
Incidentally, the clock testpoint mentioned in the manual is one of the
digit strobes. That's why it's a division of 3 from a power-of-2
frequency. And that's what 'gave it away' when I was sorting out just
what was going on on that board.
The clocks are fairly common, ones that have not been damaged by battery
electrolyte less so (but they can generally be repaired). 16 bit parallel
interfaces are really common, but the versions with particular I/O
cables, other thnn the Option 085 one for the 8" floppy are much rarer. I
am still looking for wire- and jumper- lists for all the optional cables.
Have you seen a metal-cased I/O module for these machines? One of my HPIB
interfaces is in a die-cast case, not a plastic one.
-tony