Floppy controller questions

Dave Dunfield dave04a at dunfield.com
Tue Aug 23 21:22:53 CDT 2005

>That's what I wanted. I don't have any 8" drives, so adding support for them
>is pointless. Ideally, I want a board that has a 6502-type interface on one
>side and a 34-pin IDC connector on the other, with support for most common FM
>and MFM 3.5" and 5.25" formats.

I did a fairly simple 765 based controller in my D6809 which does 5.25" DD
disks (should work ok with 3.5" DD) - it has a 6809 bus on one side and a
34-pin connector on the other. It was designed mid-80's, and uses a 765, 9216,
LS175, LS153, LS161, LS174, LS139 as well as floppy bus drivers/receivers, and
a couple of LS04 gates and one LS00 gate borrowed from elsewhere in the system
(The whole computer was one big wire-wrap board - you can see it on my site).
I don't pretend it's the most efficient design, but it was (relatively) low
parts count and worked well for me - you are welcome to it if you want it.

>I managed to get DMA-mode transfers working, but never managed to get polled-
>mode or interrupt-mode transfers working. Guess I'll have to learn fast when
>I start writing code to drive the FDC...

I did polled drivers on the 09 and it worked well. One thing I did find was
that I had to connect a select to the TC pin so that I could pulse it to end
a transfer - I did not find a way to cleanly end a transfer in polled mode
without TC. I can give you the 6809 driver code as well if you want it.

dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Collector of vintage computing equipment:

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