LVD Release Glitches

John Lohmeyer - SCSI jlohmeye at Symbios.COM
Fri Jan 19 15:35:57 PST 1996


* From the SCSI Reflector, posted by:
* <John Lohmeyer - SCSI <jlohmeye>>
It appears that this message didn't actually get posted to the reflector.
Sorry if it is a duplicate.  -- John Lohmeyer

Forwarded message:
Date: Thu, 11 Jan 96 11:12:58 PST
From: wally at eng.adaptec.com (Walter Bridgewater x2371)
Message-Id: <9601111912.AA06877 at eng.adaptec.com>
To: scsi at symbios.com
Subject: Re: LVD Release Glitches
Cc: jimlie at eng.adaptec.com, yeshwant at eng.adaptec.com, chrisb at eng.adaptec.com,
        simonn at eng.adaptec.com


I really like the idea of having symmetrical output waveforms for
LVD SCSI, I think it would help a lot with set/hold timings and
noise margins.

But, I don't think it will help the release glitches.  As discussed
in Monday's LVD SCSI study group, dropping the current on negation drive
would lower the glitch level, but, the other direction of the
specification to only have a minimum drive current or voltage,
says that you can have more output current, which will still have
a big glitch.  So I don't think the idea at the end of the meeting
on Monday will work.

I agree that we should try to fix this problem in the protocol or 
logic design part of the controller.  
And, not to prohibit drivers from turning off slowing to prevent glitches.
As, the protocol should also work if you don't get the glitch.

Wally 





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