speaking of 3.5

Thanks for all the comments and suggestions on this topic guys. I appreciate it. Indeed the goal was to connect a 5.25" or 3.5" drive with soft-sector media to an H89 and to my SWTPC 6800 which has a Pertec controller (nearly same design as the H89, using a USRT as the floppy controller) and then emulate the 10-hole hard sector media that each requires. The follow on project was to emulate 16-hole hard sector for a Micropolis controller I have in a homebrew CP/M system. I clearly need to be much more synchronous with the speed of the media than I had anticipated. So, the first change to my design will be to keep the drives selected and with motor on all the time and then my microcontroller can track the index pulses. Dwight makes a good point about the leading edge vs the trailing edge of the index pulse and I will explore that behavior too. My fatal mistake so far was assuming that the 3.5" drives and media were much more accurate in their speed than older 5.25" stuff. It's clear now that that's not the case. w.r.t. completely emulating the drive electronically with no moving parts, the "SVD", http://www.thesvd.com/SVD/ has a big following in the Heath H-8 / H-89 world and I do have a couple of them to play with. That's certainly the most practical way to solve this problem... But I wanted to mess around with floppies still since they seem more authentic to the usage model of these older machines. I went down the 3.5" path because that media is still easily obtained and I have hundreds and hundreds of pieces on hand anyway. Chris