AnsweredAssumed Answered

vrf Logical unit numbers

Question asked by VRFuser on Jun 16, 2004
> When I assumed the responsibility of maintaining our test systems,
> I was told that the logical unit numbers were selected from a
> recommended list from HP (now Agilent).

As far as I'm aware (and anyone please correct me if I'm wrong) these
numbers come from seriously ANCIENT hardware and have nothing to do with
recent times.

Your Series 80 HPIB pods came set to ISR 7 and the PIO pods came set to ISR
6. Serial was 9. There was a little dial on the back that you could turn to
different numbers, but hardly anybody ever did. This scheme was simply
perpetuated down the ages to IO Libs (and that's about the right term -
ages - we're talking about more than 20 years ago).

These numbers have really no meaning what so ever, except for the magic
number 14. By default, this number is reserved (or something like that) for
NI hardware. I have exactly one example of using NI hardware in an otherwise
HP/Agilent test system and it works fine at 7. Les or Jay can probably shed
some light on 14. I stay away from it. I've had troubles with LU14 when
assigning a large block of serial ports so I start them at 21 instead of 1.
-SHAWN-


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