8 Apr
2007
8 Apr
'07
10:51 p.m.
Jules Richardson wrote:
This is a 3.5" DSHD drive. It works fine on my BBC Micro, which is what's
confusing me, because on a breadboard it's not doing anything. It's as if the
drive isn't even connected, but continuity checks out fine.
That's weird. That's three of us separately
suddenly fiddling with this
again (personally I suddenly stumbled across enough SRAM the other day
for a raw, over-sampled track buffer, which rekindled my interest in
actually Getting Something Done).
I just needed a spare time project to help keep me sane. What with all the
university work I *should* be doing... :)
- All I/O
lines from the floppy raised to +5V via two 4k7 resistor
packs
Hmmm, the SA-400 manual says that the lines should be terminated by 150
ohms to +5V on the last drive in the chain. Output line 'true' from the
drive is logical zero, 0.0V to 0.4V, 48mA maximum. Output line 'false'
is logical one, +2.5V to +5.25V, 250uA maximum. Doubtless the manual's available in electronic
form somewhere on the
'net - probably on Bitsavers.
Yes, I've seen the SA400 manual, and a few of the Tandon 5.25" drive manuals.
What I haven't seen are any manuals that cover 3.5" drives, though I suppose
99% of the interfacing stuff is the same.
I did want to get a primitive MFM data-separator working tonight, but I've
spent all afternoon scratching my head over this and come up with nothing.
300RPM would be a 5Hz pulse rate, 360RPM would be 6Hz,
so a bit more
than that.
Which should still be enough to make my logic analyser display the 'toggling
line' image in the input map display instead of 'stuck high'...
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