4 Mar
2002
4 Mar
'02
11:59 a.m.
There are several versions of the '80x manual, but, unless I completely miss
my guess, at least one of mine has pin 2 defined for RWC. Now, several of the
implementation instructions for the old "radial" options use that same line,
telling you to cut it free before using it for radial ready or radial index,
or whatever.
It would be really interesting to know which version of the drive the Intel
folks intended to be used here. For most purposes, the RWC signal generated
internally by the drive itself is perfectly adequate for detecting track 43,
thereby freeing up the signal on pin 2, but only the later versions of the
Shugart drives used that. The connection to pin 2 was removed from the doc's
at about the time that they stopped using a negative supply, IIRC.
Needless to say, it would be interesting to know whether this controller board
even uses the head select signal that requisite for two-sided operation.
Dick
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, March 04, 2002 4:48 PM
Subject: Re: Need Shugart 851 manual
> 10 16 Track <43 (is this
really track > 43 ???) >>My
> docs say "< 43" also.
>
> Shugart says that pin 16 is an "alternate I/O" connector and it can be
> used for whatever the manufacturer decides. I've checked and it does
> connect back to the drive controller. So it's something else that I have
to
investigate.
Interestingly, The SA801 service manual I have makes no mention of any
track>43 or reduce write current input. So either Intel did something
very unconventional to the drive, or the line isn't really Track>43...
Tracing the signal from the manual is hard because Intel are not
consistent about the pin numbering on connectors (in some cases, 2 mating
connectors have different pin numbering schemes), and they seem to have 2
different conventions for the Blue Ribbon connectors _on the same
diagram_. But it does appear that the Track>43 signal on sheet 1 of the
interface board schematic really does end up on pin 16 of the drive.
What's the part number on the SA801 logic board you have, and what (if
anything) is connected to the 'D' jumper?
Incidentally, the 7485 comparator for the binary-coded drive select lines
is shown as 'customer installed option' in the SA801 manual.
-tony