8" disk drive project - test-drb@ccmp.vtda.org

6 Nov 2007

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Subject: 8" disk drive project
   From: Grant Stockly <grant at stockly.com>
   Date: Mon, 05 Nov 2007 22:04:47 -0900
     To: cctalk at classiccmp.org

I want to use a QUME 842 or SA800 in an altair disk subsystem.

Both seem to have the same interface.

The FD400-5x0-5x1 manual seems to show the drives being quite similar.

The first thing I see is that there are extra signals.

"Trim Erase", "Write Enable", and "Write Data" where the
Shugart 
interface only has "Write Data" and "Write Gate".  I assume that gate

and enable are the same thing.  The FD Pertec drives also have "IN", 
"OUT", and "STEP" instead of "STEP" and
"DIRECTION", but that is not 
a big deal.  That can be generated in software. 
Trimerase is usually jumpered to Write-enable.  

...
 What I don't see is any input to perform the
function of head 
current.  How does the shugart interface handle this? 
Not all drives required or used it.

...
 Can I ignore the trim erase feature?   
No.

...
 How do I generate a write busy 
signal?  I'm willing to make some circuits to fake these signals if required. 
Write busy is easy set a oneshot on write enable and use the output as 
a response.  If you think about it why sould you need write busy if 
your busy writing?   However some used that as a Door lock signal
to prevent opening a door during write.

The 8" interface world is generally complicated by difference names,
pinouts and signals for the same or very similar signals.  That and 
just as many signals and options that go unsued or just not required.

Allison

...
 Thanks,
Grant 