SPI Command IU CDB clarification

Sudhanshu Mittal smittal at tripace.com
Wed Sep 6 03:57:20 PDT 2000


* From the T10 Reflector (t10 at t10.org), posted by:
* Sudhanshu Mittal <smittal at tripace.com>
*
Is this limited to CDB field only? I got same kind of confusion at SPI L_Q
information unit also. I think all the places which mention MSB/LSB should
be clarified in order to remove any possible confusion.

Sincerely,

Sudhanshu Mittal

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  -----Original Message-----
From: 	gop at us.ibm.com [mailto:gop at us.ibm.com]
Sent:	Wednesday, September 06, 2000 2:01 AM
To:	t10 at t10.org
Subject:	Re: SPI Command IU CDB clarification

* From the T10 Reflector (t10 at t10.org), posted by:
* gop at us.ibm.com
*
Gerry is correct the op code will be in byte 4. The notation used is the
same as though out all the SCSI standards. However, in this case, I can see
where there may be some confusion because the CDB format consists of
several fields. I would have no problem removing the MSB and LSB in the CDB
field it there is a general agreement that it would help.

Bye for now,
George Penokie

Dept Z9V  114-2 N212
E-Mail:    gop at us.ibm.com
Internal:  553-5208
External: 507-253-5208   FAX: 507-253-2880



Gerry.Houlder at seagate.com@t10.org on 09/05/2000 05:31:27 PM

Sent by:  owner-t10 at t10.org


To:   t10 at t10.org
cc:
Subject:  Re: SPI Command IU CDB clarification



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

The op code will be in byte 4. All of the CDB bytes are intended to be in
the same order as FC packets and parallel SCSI bytes in existing
implementations.

I'm not sure what your MSB/LSB confusion point is. Perhaps it is because
SCSI interprets these as Most Significant Bit and Least Significant Bit,
respectively, instead of Byte. Most significant bits are only valid within
a particular field or parameter and has no meaning across multiple fields.





"Day, Brian" <bday at lsil.com>@t10.org on 09/05/2000 04:08:57 PM

Sent by:  owner-t10 at t10.org


To:   "'t10 at t10.org'" <t10 at t10.org>
cc:

Subject:  SPI Command IU CDB clarification


* From the T10 Reflector (t10 at t10.org), posted by:
* "Day, Brian" <bday at lsil.com>
*

I've had another engineer interpret the CDB field differently than I had in
the SPI command IU CDB field.  The MSB/LSB notation was a little confusing.

The CDB field is defined at bytes 4 through 19 in the Command IU
(referencing Table 35 in SPI-3).  I've always thought the Operation Code
for
that CDB would be located byte 4, which would be the first byte of the CDB
to get transferred across the bus.  However, my colleague interpreted it to
be byte 19 because of the LSB notation.

As a specific example, if an initiator was sending a 10-byte WRITE command,
does the 0x2A come out on byte 4, or byte 19.

Can someone please clarify....

Brian Day
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