WD style: no problem with index pulse timing relative to data NEC765
style: index pulse is necessary during LLF, but may need to be
blocked during read/write, although a few of the newest drives may
not be happy without index.
On Sat, 28 Nov 2015, Chuck Guzis wrote:
765/8272 are particularly bad in this respect (they're blind for a full
millisecond or so) in contrast with 765A/8272A, which chopped the blind spot
by half.
In the 8272 days, I added a one-shot to delay the blind spot by a varying
amount, which solved the problem neatly, while still allowing the index to
pass through.
The index is also needed for WD17/27 family controllers also for LLF. Ya
gotta start (and end) somewhere.
Yep.
Need index for LLF, but not necessarily for read/write, albeit with a few
complications
If you simply block index with the 765 type FDC, you'll never get a "sector
not found" error--if you have a deadman timer, it'll expire.
Exactly. It will time out, and get a time-out error instead of the
requested sector not found.
