Changes for SPI X3T10/94-038 Rev 3

Paul D. Aloisi 603-429-8687 aloisi at
Sun May 22 14:20:01 PDT 1994

This is the out come of the X3T10/94-038 Rev 2 presentation in the 
18 May, 1994 SCSI working group meeting, and follow up individual 
negotiation meetings.

Slide one corrects some of the hot plugging issues that have arisen
in the implementations.

Slide two addresses slewing problems that would occur if Voh is
left unrestricted. Slewing from 5.25 Volts would either create too
fast of a fall time or too long of a slew time. The first section
addresses the driver, the second section addresses a parameter 
that was left out of the Terminator specification. 

(Text Version of the Slides)
X3T10/94-038 Rev 3

(Slide 1)
Proposed Changes to SPI

Annex A.3 and A.4 Change
d) The SCSI device being removed or inserted shall employ 
transceivers that conform to the requirements for glitch-free 
power on/off in 7.1.2 and 7.2.2. The SCSI device shall maintain the 
high-impedance state at the device connector contacts during a power 
cycle until the transceiver is enabled. Power cycling includes on 
board termpwr cycling, caused by plugging, and device power cycling 
caused by plugging or switching. Note that any on board switchable 
terminator as well as the device transceivers may affect the 
impedance state at the device connector contacts.

Annex A.4 Addition Limit Termpwr Bypassing
g) Bypassing capacitors connecting to the termpwr line on the device 
being inserted or removed shall not exceed 10 uF. For single-ended 
applications, bus termination shall use voltage regulation on both 
ends (Reference SCSI-2 Alternative 2).

Slide 2
Voh Issue

7.1.2 Voh allows 5.25V Maximum, Add Note 8

Note 8 With these specifications voltages greater than 3.24 can 
not be directly driven by the driver, but voltages above 3.24 
may occur as reflections.

7.1.1 Single-ended Termination, Add f

f) The terminator shall not source current above 3.24 V d.c.

More information about the T10 mailing list