Wording issue with SPI-4 rev. 8

Gerry.Houlder at seagate.com Gerry.Houlder at seagate.com
Fri Dec 28 13:09:30 PST 2001


* From the T10 Reflector (t10 at t10.org), posted by:
* Gerry.Houlder at seagate.com
*
I am looking at SPI-4, revision 8. The way I read it, there seems to be a
conflict between the footnote in Table 7 in section 4.12.4.4 and the last
two sentences in section 4.12.5 (just prior to Table 11).

Table 11 lists the "Valid negotiable field combinations".  The two
sentences that precede it say:
   "Only the combinations in table 11 shall be allowed.  All other
   combinations of the listed fields are reserved."

The first data line in Table 7 says that a REQ/ACK offset of 00h:
     "Specifies asynchronous transfer agreement. (superscript: a) "
The (superscript: a) superscript footnote says:
     " (superscript: a)  Transfer period factor and protocol options other
than QAS_REQ shall be ignored."

I see two problems with the footnote:
(1) It says that "protocol options other than QAS_REQ .." have a certain
handling. I believe that QAS_REQ should have the same handling as the other
protocol options because QAS isn't allowed with asynchronous transfers. It
is only allowed with Information units, which are never asynchronous.
(2) It says that ".. shall be ignored." Ignore suggests that the responding
device can send the same values back to the initiating device. However the
wording with table 11 say "only the combinations in table 11 are allowed".
This suggests that the responding device must clear the invalid bits in the
responding message or it would be transmitting a reserved combination.

I suggest rewording the footnote to say:
     The Transfer period shall be ignored and the protocol options shall be
cleared.

Does anyone else have an opinion on this?

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