[Techtoolslist] Fluke 9100 disk change

[Tony Jones]

Hi.

I'm not expecting anyone will know the answer to this (I get the
feeling few own a 9100 and fewer make much use of it) but I'll ask
regardless, hope springs eternal.

Does anyone know of a use case where the 9100 system software requires
that the disk change feature functions correctly?  What's the "disk
change feature" you might ask?  There is a test for it in section 4-75
of the 9100FT service manual.   Basically when the disk is changed an
interrupt is raised through DTIO#2. The test in the manual is
basically that subsequent iterations of the same operation should not
access the disk unless the disk has been changed between iterations.

However I'm not aware of any part of the software that relies on this
feature working. When loading the system sw from multiple floppies,
there is a manual keystroke required to flag a disk change.

It's interesting how this is implemented on 9100.  For drive 1 it;s
handled on pin 14 of the floppy cable,  which per the Shugart standard
is normally DS2.  For drive 2 it's handled on pin 4 on the 9100A and
pin 2 on the 9100FT (though it's jumperable back to 4).   The line is
held low whenever a disk is inserted and held high whenever ejected.
The Shugart 34 pin standard has diskchange on pin 2 but the semantics
of it's signal are totally different, it only changes after a
stepping.

It's also interesting that the disk change test doesn't work correctly
when the firmware is configured for a Sony floppy.  It does when
configured as a Canon floppy.  I suspect this is why Jon (Porchy)
needed to ground pin 14 to get his HxC USB floppy emulator to work.

Thanks

Tony