31 Dec
2007
31 Dec
'07
7:37 p.m.
Date: Mon, 31 Dec 2007 18:07:38 -0500
From: "Andrew Lynch" <lynchaj at yahoo.com>
The different signal is called a "constant
index" signal. Apparently, it
is similar to an /INDEX signal from a floppy drive interface but the
signal tells the HD controller everytime sector 0 passes around. The HD
controller requires it for setting up the PLL.
Here is an excerpt on the subject from the VG engineer:
Well, the ST506 knows nothing from sectors--it's about as "bare" and
interface as they come. I wonder if by "constant index" it's meant
that there's always an INDEX/ signal present; not just when the drive
is selected. At least that would make sense from this:
All hard drives working with a Vector FD/HD must have
constant
index. There is a phase locked loop that is controlled by U20 which
is CMOS 4040 chip and unless you have constant index the PLL never...
Maybe? What happens if the drive is jumpereed so as to be
permanently selected?
Cheers,
Chuck