Drive # vs. select #

10 views
Skip to first unread message

snhi...@gmail.com

unread,
Apr 3, 2026, 1:43:57 PM (14 days ago) Apr 3
to MFM Discuss
Hi, all.

What is the difference between numbers reported for drive vs. 'select'?  I'm seeing repeated messages about 'select 3', but the emulator and host are setup for drive 1.  I can see where it's coming from in the source code, but I'm not up on the PRU internals.

David Gesswein

unread,
Apr 4, 2026, 9:13:50 AM (13 days ago) Apr 4
to mfm-d...@googlegroups.com
Select is the select lines on the interface. The encoding changes
with board revision. For A & B its the 4 select lines. I would need to look
further to see which bit is which line. For C & D its two bits for the two
select jumpers. Upper bit is drive 2 jumper and lower bit drive 1 jumper.
Signals are active low and board uses non inverting buffers. The print
exclusive ors the value with one so converts to active high. That means
3 is both select signals are active.
> --
> You received this message because you are subscribed to the Google Groups "MFM Discuss" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to mfm-discuss...@googlegroups.com.
> To view this discussion visit https://groups.google.com/d/msgid/mfm-discuss/9ae1945e-00db-48f7-85cf-ce8a8875390fn%40googlegroups.com.

Reply all
Reply to author
Forward
0 new messages