> The Index Mark is a single small block of data recorded on the disk,
> that occurs once per track, right after the index hole; it's NOT the
> index pulse from the hardware, and NOT a sector header and it is
> optional. Lots of controllers don't put it there unless told to.
> Given that any sensible controller will see the index pulse from the
> drive interface, the Index Mark pattern is unneccessary -- but some
> controllers do expect to see it.
Thanks very much, I had not relaized that there was a differens between
the Index Address Mark and the ID Address Mark. Now it all makes perfect
sense.
Now for antoher question:
On a typical 5.25" drive how long does the Index Pules usually last?
The wd177x and wd179x data sheets don't expliciatly say. But it infers
that is lasts about 60 byte times in MFM mode.
Also I see that a single byte time in MFM is about 2 microseconds, that
suggests to me that the index pulse last about 120 microseconds. Is that
correct?
--
tim lindner
tlindner_at_ix.netcom.com
Received on Sat Dec 27 2003 - 18:11:06 GMT