Ultra SCSI-2

Jim McGrath jmcgrath at qntm.com
Tue Oct 3 10:48:21 PDT 1995

        Reply to:   RE>Ultra SCSI-2

I do not think this is covered in detail yet, but the line people look at is
DIFFSENS (i.e. the mode is not selected by the system per se).  The real
interesting point is not power on (since the timing will probably take
care of itself), but hot plugging (since a system can go from LVDS back
to single ended).


Date: 10/3/95 9:32 AM
To: Jim McGrath
From: Lee Cleveland
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Date: Tue, 3 Oct 95 11:22:46 CDT
From: "Lee Cleveland" <lcleveland at VNET.IBM.COM>
To: scsi at symbios.com
Subject: Ultra SCSI-2

I have been reading the SCSI SPI-2 Low Voltage Differential (Paul D Aloisi
Unitrode 10-July-1995) and in it it states that :

It is the intent that controllers will be built that can drive both low
differential and single ended depending on the bus configuration. If all of
the devices are low voltage differential then the system will run on low
volatge differential, but if on device will not then all devices revert back
single ended. This will allow backward compatibility with forward migration

The question:

Is there any more documentation that describes a POWER up sequence where all
devices assume singled ended and at some point switch to differential
based on the system letting everybody know?



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