19 Mar
2004
19 Mar
'04
3:07 p.m.
If you're
just talking to 1 or 2 peripherals (say you want to hook up a
GPIB plotter, or you want to get the data off an HP disk drive) you can
get away without the special buffers. You can use open-collector TTL
gates to drive the bus, and TTL schmitt triggers ('14s, for example) as
receivers. Like many things I'd not do this on a 'production' board, but
it works as a hack.
Interesting... I had not thought of substitute line drivers, but it makes
sense... unless you are trying to build a gargantuan PET system (the kind
nobody could afford "back in the day"), most people had one disk drive box
(2040/4040/2031/8050...) and _maybe_ a printer. These days, though, the
most common thing for Commodore owners would be to hook up a disk drive
to a modernish machine to extract floppies... using O.C. drivers and
Schmitt trigger receivers would work just fine for that. I have plenty
of GPIB-capable machines from handheld calculators up to
workstations (e.g. HP41 + HPIL + HP82169 translator in the first case,
PERQ in the second). I even have the Acorn interface for the Beeb.
Nothing spare, though
With one exception, all of my GPIB hardware is C= or third-party for
C= CPUs... I do have one HP 9-track tape drive with a GPIB interface,
but I've never even powered it up. I should Google for some information
on it when I get home... I have no idea how much buffer space it has
onboard, or if you could drive it at the incredibly slow software-driven
C= data rates, but it'd be cool to put a 9-track on a PET! I'm sure