SFF-8636 -- Common Management Interface

[Felton_Mickey at emc.com]

* From the T10 Reflector (t10 at t10.org), posted by:
* <Felton_Mickey at emc.com>
*
Amit- 
As a system provider, I'm in favor of the current scheme as I need to buffer
each port for isolation. Isolation is far more important than pin count...As
this bus is now becoming critical for usage rather than just informative.
(because of the buffer length requirements)
I'm also in favor of the reserved pin as it gives more options for system
usage.
-Mick
________________________________
From: owner-t10 at t10.org on behalf of Shah, Amit M
Sent: Tue 5/25/2010 2:34 AM
To: barry.olawsky at hp.com; endlcom at acm.org
Cc: t10 at t10.org
Subject: RE: SFF-8636 -- Common Management Interface
Hi Barry / Dan,
I believe you are the owners of the SFF 8636 and SFF 8449 proposal. Can you
please throw some light on the interface requirements as mentioned in the
original email.
I share the same concerns as Curtis...regarding use additional silicon pins
to solve the concerns related to multi-drop. I am sure that there would have
been some good arguments that must have led to this requirement. Just want to
better understand the motivation behind  the fixed addressing architecture.
Also Can you throw some light on Interrupt? Can it be shared across multiple
interface?
Thanks,
Amit Shah
From: Ballard, Curtis C (StorageWorks) [mailto:curtis.ballard at hp.com] 
Sent: Friday, May 21, 2010 7:57 AM
To: Shah, Amit M; t10 at t10.org
Subject: RE: SFF-8636 -- Common Management Interface
I had the same question on point 1 and talked to one of the members working
on that specification.	The response I received was that with the multi-drop
interface it was possible for one device to completely lock up the bus and
prevent access by any other devices if that device didn't play nicely or had
a fault.  Having worked with I2C in the past and seen that behavior I can
appreciate that concern but it would be nice to have multi-drop capabilities
so devices with a lot of external ports don't have to have multiple
management interfaces or a MUX.
Curtis Ballard
Hewlett Packard
StorageWorks Platforms Tape
Fort Collins, CO
(970) 898-3013
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Shah, Amit M
Sent: Friday, May 21, 2010 12:29 AM
To: t10 at t10.org
Cc: Shah, Amit M
Subject: SFF-8636 -- Common Management Interface
Hi,
I had couple of question about the proposal "SFF-8636" related to Common
Management Interface.
1.	  This proposal talks about 2 wire management protocol which is sort
of similar to I2C. The Slave Addr is fixed at 50h. This means that the
interface cannot be used as a multi-drop interface and each cable will need
its own individual interface. So  the question is that why a multi-drop
interface was not considered for common management interface?
2.	 The Spec also talks Interrupt. Also SFF-8449 talks about IntL. Can
this Interrupt be shared across multiple interfaces?
Will appreciate your response.
Thanks,
Amit Shah
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