Shurgart drive question

From: Richard Erlacher <richard_at_idcomm.com>
Date: Wed May 24 19:22:22 2000

Are you using a controller that requires the external "data separator" on
the drive? If you use it with a controller that expects the raw data you'll
get something that works part of the time. One might interpret that as
being pattern-sensitive, since it is.

I'm not sure you need to fiddle with this data separator much, but if you
take into consideration that what most folks call a "data separator" is
really a clock extractor, which is little else than a missing clock detector
and fills in the missing clocks for the benefit of the data extraction logic
in the controller.

Why not contact me off-list and I'll look up what I can from the drive
documents.

What troubles me is that I don't know what kind of controller you're using,
hence I dont know that this mechanism on the drive is even required for it.
Are you sure you need this crude bit of circuitry?

Dick
----- Original Message -----
From: Dwight Elvey <elvey_at_hal.com>
To: <classiccmp_at_classiccmp.org>
Sent: Wednesday, May 24, 2000 12:19 PM
Subject: Shugart drive question


> Hi
> I'm still working on my NIC-80. I'm having a data pattern
> sensitive problem. I'm not yet sure if it is in the SA900
> drive or in the controller. When looking at the drive,
> there is a clock/data separator circuit. It uses two one shots.
> One is for the next clock cycle after a one was read and
> one is for the next clock cycle if there was no one read.
> I understand the issues of this shifting of the read
> data but I don't know how much these two one shots need
> to be adjusted. The SA800 TTL board also has the same circuit.
> I was hoping that someone with an old drive could put
> a 'scope on these two one shots and determine the nominal
> pulse widths they see? The test points are labled the same
> on both the SA900 and SA800 series drives as TP21 and TP24.
> They are negative going pulses.
> Dwight
>
Received on Wed May 24 2000 - 19:22:22 BST