[time-nuts] Off the wall: anyone with experienceprogrammingHP3456A?

John Miles jmiles at pop.net
Sat Sep 10 15:20:11 EDT 2005

The unfortunate truth is that GPIB is actually a pretty flaky thing.  It
seems there is always a certain amount of swing-a-dead-cat empiricism
involved with getting any complex GPIB hookup to work reliably.

I can't talk to my Tek 492AP SA unless I turn on the 8566B or the 8657A that
shares its GPIB bus, for instance, and I am fairly certain that all of my
hardware and cabling is in good shape.  I've run into many little hangups
like this over the past few years.  None of them have been showstoppers, but
none of them have made me think too highly of the GPIB spec as a robust
communications mechanism, either.

It is very possible that one 5370B may have problems in a particular GPIB
configuration that will not show up in another configuration.  Someone has
already noted that there were a couple of different firmware releases for
the 5370 counters that addressed GPIB support issues.

It seems wise to keep GPIB programs as simple as possible, using as few
features as you can.  Whenever I've tried to get fancy, I run into trouble.

-- john, KE5FX

> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of Poul-Henning Kamp
> Sent: Saturday, September 10, 2005 11:24 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Off the wall: anyone with
> experienceprogrammingHP3456A?
> In message <4323228B.7040401 at febo.com>, John Ackermann N8UR writes:
> >In theory, the bus is supposed
> >to handshake to avoid that problem, but that's not always reliable on
> >the older instruments -- they will report that they're ready for another
> >command when in fact they aren't.  In fact, while doing this experiment
> >the 5370B would show "Err 1" (invalid command) on its display if I tried
> >to talk to the 3456A too soon after talking to the 5370.
> Are you 100% sure this is a problem on the 5370B ?
> I've spent a lot of time with my logic analyzer while implementing
> GPIB in FreeBSD (partly because I couldn't find a datasheet for the
> uPD7210 anywhere) and I have never seen my 5370B misbehave in any
> way.

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