Re: HPIB bus commands

From: Larry Mollica (
Date: 2004-04-13 21:01:31

Quoting Nicolas Welte:

> Hi Larry,
> I assume the commands you need to send are single byte commands only.


> In this
> case, you can make use of the "send secondary" ROM code, which sends bytes
> under ATN control onto the bus, very probably after addressing the device.
> Normally this byte is in a certain range, with the higher bits selecting a
> CBM command (e.g. open or close) and the lower bytes being the actual
> secondary address. I think bytes in the range $00-$1f are not used in the CBM
> syntax, but they are used for standard GPIB messages. Still it should be
> possible to make the CBM ROM send those bytes. If this is what you want, I
> can try to find a ROM entry that you can use.

Some sort of ROM call would probably be ideal.
If I follow you, the ROM code you are taking about is the piece that's normally
used to send a secondary address(?), and you are thinking it might be exploited
to put out a bus command. That would be slick if it works out. Unfortunately my
skills are limited to BASIC, so any pointers on this would be very welcome.

>Do you prefer BASIC 2 or BASIC
> 4 for programming? For some reason I know that you have available both in
> your PET ;)

We are using BASIC 4, and the hardware is working just fine, thank you very

> I didn't do measurement device programming for quite a while, but I think I
> remember that commands like e.g. unlock can also be sent as a text command
> without ATN. But maybe I'm wrong.

Of the 4 or so  pieces of gear we've worked with, they all seemed to want bus
commands to unlock. We have tried sending the listed bus commands via PRINT# to
the instruments, to no effect.
I don't have the HP manuals handy right now. The instruments we are working with
are HP RF gear, like signal generators and spectrum analyzers. There seems to be
some bus commands common to all of the HP RF gear I've seen so far, the one I
recall is ASCII "?" (most of the HP doc's seem to want to express everything as
printables or octal), which sent as a bus command will release (as I recall).
Some are bus commands are "universal" as in they will be obeyed by all HP gear
on the bus, regardless of whether or not it had been addressed (I think "?" is
one of those). They also have bus commands specific to the addressed instrument.
All of the HP bus commands I recall seeing are in the range of printable, or in
some cases control characters.

Larry Mollica

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