21 Nov
2009
21 Nov
'09
12:22 a.m.
Tony Duell wrote:
The 8" drive has a 50 pin interface connector, of
course, but most of the
signals are the same as the SA400 interface. The main differences (from
what I rememer) are that the 8" drice may separate index and sector
pulses for hard sectored disks, it may have an interal data separator for
single-density disks, and it will have a TG43 input to reduce write
current on ther inner cyliders.
!REDWC, pin 2. I've made pin 2 an I/O on my analyser -- it can either be
read (pullup enabled), floating, or pulled low. Thus, you can poll the
disc's type (if REDWC is used as a "high density" output), or apply
density selection, or use it to drive TG43, depending on what the drive
requires.
The 3.5" disk doersn't have an index hole in
the sense that the other
floppies do. You can't have a 'hard sectored blank disk', for this
reason. I suppose it would be _possile_ to make a drive that produced
multiple index/sector pulses per vevolution, but I've never seen one.
That's effectively the question I was asking -- the discs don't support
it, so did anyone bodge a PLL onto a drive to do it?
It does look like someone's had a go at something similar to what I was
thinking of: http://www.lesbird.com/sebhc/storage/storage.html
Look under the heading "Hard Sector Floppy Emulator".
You can alos support 3" drives/disks. The Hitachi
drives have a standard
34 pin SA400 interface, the ones that Amstrad used have a 26 pin
connector (IIRC) with the same signals on it. 3" disks do have an index
hole, the sensor is a light barrier there, not a signal on the spindle
motor, but I've never seen or heard of hard sectored disks.
So more or less the same technology as a 5.25" disc then -- a ~5mm hole
in the jacket, a ~1mm pinhole in the disc, and an optosensor in the drive.
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/