ATN on SPI L_Q for commands

Gerry.Houlder at seagate.com Gerry.Houlder at seagate.com
Wed Apr 4 07:20:27 PDT 2001


* From the T10 Reflector (t10 at t10.org), posted by:
* Gerry.Houlder at seagate.com
*

Yes, the raising of ATN is the way for the initiator to "change its mind".
The mechanism is intended to allow the initiator to send initiator Detected
Error message to the target. The standard doesn't have a firm definition of
why an initiator would do this (the standard has always been lenient on
describing why initiators would to anything) but the usual cases cited are
parity or addressing error on initiator's internal bus, a higher priority
task wishing to abort the current task so it can get immediate access, or
test software written by a very picky test engineer.





Sriram Srinivasan <srirams at lsil.com>@t10.org on 04/03/2001 08:27:14 AM

Please respond to Sriram Srinivasan <srirams at lsil.com>

Sent by:  owner-t10 at t10.org


To:   t10 at t10.org
cc:

Subject:  ATN on SPI L_Q for commands


* From the T10 Reflector (t10 at t10.org), posted by:
* Sriram Srinivasan <srirams at lsil.com>
*
  Can someone tell me what is the expected target behavior when the
initiator asserts ATN on a SPI L_Q with a "Multiple Command" or a "Last
Command" type?  Figure 74 (section 14.2) shows an arrow named "Attention
Condition" from the SPI L_Q out to MESSAGE OUT ... and section 12.2
states:

  "g) .... the target shall enter the MESSAGE OUT phase at the
completion of the current SPI information unit"

  So is this a way for an initiator to "change his mind" after sending
an L_Q to assert ATN and make the target get out of the command flow?
The SPI L_Q is being sent from the initiator, so HE is not the one
detecting iuCRC errors, then why assert ATN on this SPI L_Q?  Other than
section 12.2 and figure 74, there is no other place where SPI mentions
what the target is expected to do after it receives the message.  Go BUS
FREE, because all he got was a SPI L_Q and did not have any Command IU
to go with the nexus?!?

  Please clarify,
  \Sriram\


----------------------------------------------------------------------

 Sriram Srinivasan                       Sriram.Srinivasan at lsil.com
 ASIC Design Engineer, LSI Logic,
 2001 Danfield Ct.,                      Phone: 970-206-5847
 Fort Collins, CO 80525                  FAX  : 970-206-5244
----------------------------------------------------------------------

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