HP-IB disc drive emulation program available

[Tony Duell]

> 
> > >
> > > > I still think it would be a useful project for somebody to make a
> > > > HP-drive-emulator. Mot using a PC, but using a microntroller, HPIB
> > > > buffers, the minimal (if any) logic you need to handle HPIB, and a CF
> > > > card. Make it 'open( and I'll build several...
> > >
> > >     What does a HPIB buffer contains that cannot be reproduced with
> > > digital/analog circuitry? :oO
> >
> 
> About two years ago, I did some work on such a project. I built a very crude
> serial -> HPIB "controller" using an AVR microprocessor and a couple of

It's not hard to make a GPIB interface without using a special decoder 
chip. I uilt a triival HPIB-Centronics interface (to run a parallel 
printer from a PERQ) usign a couple og 16V8 GALs and a few TTL buffers. 
And it's been doneby bit-banging many times.

IIRC most of the handshakers are 'interlocked' so the software can take 
arbitrarily long to respond to a change of state of one of the signals. 
There is oen (I think only one) case where the timing is critical, which 
may ddd a couple of gates to the design.

> interface chips. I did not use a HPIB 9914 or other controller. All the
> logic was done in software. I bitbanged everything and it sorta worked. :-)

All the Commodore GPIB disk drives, printers (and indeed PETs) bit-banged 
the interface. Commodore never used any of the speical controller chips 
AFAIK. Mind you, the Commoodore GPIB is a little 'odd' when it comes to 
timing (I've seen 3rd party devices designed to link to PETs that work 
fine for that but which won't work on amost other GPIB systems). 

Even HP bit-banged it sometimes. The 82169 HPIL-HPIB translator uses an 
8049 and no HPIB interface chip. The other 40 pin package on the PCB is 
an HP buffer chip with almost no internal logic. 

> It took some searching but, I did find the correct interface (line driver)
> chips. The device ids escape me but, they might have been something like
> 75160's. They are just simple line buffers.

THere are several series of thise, I have no idea which, if any, are still
current parts (If I was designing something new, I'd want to use a part
that was still in full production, of course)

Intel made the 8298 (which I know very little about). Motorola made the 
3446, 3447 and 3448. Those 3 are quad uffers with different arrangements 
of transmit-anable lines, etc. TI made the 75160 (octal data line 
buffer), 75161 (Octal control line buffer for either devices or, IIRC, 
controllers in a signle-controller system) and 75162 (octal control line 
buffer in mulitple-controller systems). I've used the Motorola and TI 
parts, and have data sheets.

> 
> The biggest issue that I ran into was a timing issue. When a device (talker)

That may be the case I am thinking of. Maybe looking at a PET scheamtic 
would help, presumalby it can handle this provlem.

> For the multimeter this was not a problem. I attached a HPIB bus analyzer in

The HP59401 analyser is a fun toy, but I don't want it on the bus all the 
time :-)

-tony