22 Feb
2007
22 Feb
'07
4:13 p.m.
Tony Duell wrote:
Additional complexity that's not needed in this scenario.
Brent Hilpert wrote:
Let's see:
- awkward editing
- the display does not show you the instruction, you have to list on the
printer to see what you've done
- key-sequence instructions rather than expressive language statements
- very limited data-handling
- limited to no structure to the language
- etc., etc., etc., etc., etc., etc., etc., etc., etc., etc., etc., etc.
Or how about this: pretty much every lesson learned and development made in
languages and programming of the last 4 to 5 decades is missing.
I have never been fond of 'key-sequence' programmable calculators, the
'language' is not very expressive or comprehensible. In short: tortured
programming. BASIC is tortured too, but it's miles ahead of the above.
I love my HP-21, a straight-forward non-programmable 4-level-stack RPN
pocket calculator which I've had since 1976. But even back then I had no great
desire to have an HP-25 (essentially the same machine but programmable).
The weak point in this scenario however, is the
torture of programming the
9815 and problems with the tape cartridges and drive of the 9815. Those
What's wrong with programming the 9815? I thogut it was a fairly standard
4-level stack RPN machine. Given that the
plotter uses HP-GL as the control language, I began to think
along the same lines as Chuck wrote about a day ago: building a simple
parallel interface to the plotter HP-IB port that does just the data transfer
(minus all the HP-IB device selection, etc. functions) to connect it up to a
Well, the 'device selection' just means you need to be able to assert the
ATN line so you can send a command (it's sent over the 8 data lines with
the normal handshake sequence). 1) I don't know what the 'dedicated' 9815
interface on the 9872 plotter
is, but there are manuals for the ploter and interface over on
http://www.hpmusuem.net, which contain scheamtics. I think a little work
with a 'scope or logic analyser would decipher said interface (I will bet
the actual data sent is ascii-encoded HPGL, just as it is on the HPIB
interface)
The 9815 interface is essentially just what Chuck did (IIUC) and I have
suggested: the 8 HPIB data lines and 3 data-handshake lines are brought across
to the controlling machine. It's HPIB minus everything but the data-transfer.
(I do have the manual with schematic. The calculator and plotter showed up at a
university surplus a few years ago and it was one of those rare instances where
it was the just about the complete package: cables, manuals, tapes, warranty card,
and enough residual evidence to show it's lineage: used by a researcher in the
Dept. of Pathology. The pens for the plotter were missing.)
2) The HPIB (which I beluieve you have), GPIO (8 bit
parallel) and RS232
interfaqces for the 9815 all allw you to load or save a program over said
interace. You could keep the 9815 and use its HPIB interface to
communcate with some more modern machine that stored its programs, thus
avoiding the use of the tape drive and cartridges.
I noticed this in the HPIB interface manual and was thinking about doing that,
or building a flash-memory storage device. It could have a little control
panel to select a 'file' in the flash-memory. (Probably not going to happen,
as if I don't have enough projects to work on).
However, using HPIB between another machine and the 9815 is pretty much the same
problem as using HPIB between another machine and the plotter. It would be nice
as storage for the 9815 but as far as exercising the plotter goes,
the 9815 just becomes an annoying and limiting waypoint between the
newer machine and the plotter.