well I’ve got MFM flowing from the PC drive now. A couple of things:
Pins 10 and 14, the pins I’ve been using since last night, appear to be correct.
Pin 10 is the motor lead. Dropping a corresponding SX lead causes the motor to come on.
Pin 14 is the drive select lead. Although this should technically be an input as far as the drive is concerned, I’m getting a +5v from the drive. I’m measuring from a ground lead to pin 14, and getting +5 with the SX completely out of the picture. If I take this lead and short it to ground, then the drive is “selected” and it works.
If I simply cause the SX to drop its lead (pin = 0) and attach it to pin 14, this does NOT work, and the multimeter still shows +5v.
Why doesn’t dropping the SX lead cause that line to go to 0v? (incidentally, measuring the SX by itself, the lead does infact go to 0v, so the SX/programming/pin/etc is ok)
And why am I getting +5v from the drive on an INPUT pin?!@#
The pull-up resistor is amazing on the output READ DATA lead. It’s screwed up. With no pull-up whatsoever, looking at the scope shows NOTHING happening. Put a 1k (well brown black red, Im too tired to go check, but for records sake) pull-up to 5v, and bam-o I have a perfect signal. Much faster rise-times on the signal. It also looks ummmm cleaner than the amiga floppy drive. not sure why yet.
Herb sent me some good links to his site here