24 Feb
2010
24 Feb
'10
5:57 p.m.
On Wed, 24 Feb 2010, Chuck Guzis wrote:
On 23 Feb 2010 at 18:13, Steven Hirsch wrote:
Ok, so you are not conditioning the data lines? That's where I had the
notion that bidirectional buffers were needed.
--
Fair enough :-). The TTL chips of which you
speak are bidi bus
transceivers, correct? Would you use the R/W line to switch
directions, or is there other magic involved?
Any construction tips? (Schematic would be nice - but hand-waving
works, too!)
Not even that complicated. What Tony and I have been talking about
are bog-plain 7407 open-collector non-inverting buffer chips. The
floppy bus (if it can be called that) is unidirectional. So,
basically, for controller outputs, you feed said output into a 7407,
adding a small pullup (2K2 should be fine) and run the output of the
7407 to your floppies. Inputs to the controller reverse this and use
a 150 ohm pullup on the input to the 7407 from the floppy, with the
output feeding the controller (which should have its own pullup, so
none required on your part).