Data field size of intermediate data groups

Robert Frey bobf at
Wed Mar 3 11:33:36 PST 1999

* From the T10 Reflector (t10 at, posted by:
* bobf at (Robert Frey)
There seems to be a simplifying restriction, which may be common
practice, about the size of data fields in intermedidate data groups,
i.e. data groups that do not end a DT DATA IN or DT DATA OUT phase.
If the data fields in such intermediate data groups all are required
to have modulo 4 size, at least some implementations would benefit
|from reduced logic cost and improved performance. In other words only
the last data group in a DT PHASE would ever contain a (0 or 2 byte)
pad field.

Can any reasons be put forth for why such a requirement on the data
field size of intermediate data groups is undesirable? If not I will
write a proposal for future consideration.

SPI-3 Rev. 2:
> Data group format
> Each DT DATA IN phase and DT DATA OUT phase contains one or more data groups.
> A data group consists of a data field followd by a pad field, and then
> followed by a CRC field. The number of bytes transferred within a data
> group shall always be even and a multiple of four.

Bob Frey
bobf at
* For T10 Reflector information, send a message with
* 'info t10' (no quotes) in the message body to majordomo at

More information about the T10 mailing list