2 Feb
2009
2 Feb
'09
6:40 p.m.
On 2 Feb 2009 at 18:11, dwight elvey wrote:
The only timing I had was for powerup reset. Just a
cap, resistor
and diode. The rest is digital. I use an edge on diskchange
to clear and the first index to set. It isn't perfect as one
could stick a disk in and turn the motor on and then remove
without stepping. This is not likely on the Cat because
it always uses the disk for a dump ( multiple tracks ).
The Teac holds the index until ready.
Mine was for 5.25" drives; basically it waits for 2 index pulses
spaced within 10% of the nominal speed of the drive before asserting
READY. Could probably also be done with a couple of one-shots, but I
hate one-shots--and the PIC is smaller.
The nice thing is that the same PIC setup can also simulate hard-
sectored diskettes. The PICs are rated to sink/source 25 ma on any
I/O pin, not to excees 125 ma for all pins. A little dodgy for 150
ohm pullups (33 ma at 5v), but I've had no problems thus far.
Cheers,
Chuck