Question: OOB - SAS vs STP/SATA detection
Henry at scs.agilent.com
Wed Jun 16 15:27:29 PDT 2004
* From the T10 Reflector (t10 at t10.org), posted by:
* Henry Wong <Henry at scs.agilent.com>
"Shah, Amit M" wrote:
> As far as I understand the specs, the SAS spec (rev 5) has defined in
> Table-37 the min. BURST time specification. The table clearly mentions
> that a BURST "should be detected" if the burst time is more than 100
> nsec. Also it mentions that burst "may be detected" if the burst time is
> less than 100nsec. So in your case you could assume that burst could be
> detected even if burst time is less than 100 nsec i.e any transition of
> "any amount of time" could get detected as BURST.
> Also the specs mentions "The signals are differentiated by the length of
> idle time between the burst times" -- section 6.5
> That is, the OOB signal detection logic really cares about the IDLE time
> between the burst time. The IDLE time is time bound for each OOB signal
> as mentioned in Table 40 (a min. and a max. value has been defined). As
> far as the IDLE time is in the specified range and there is a valid
> BURST (any transition, could be of any duration), the hardware should be
> able to detect the OOB signaling (after "4" IDLE / BURST pairs).
> So I believe that the OOB detector logic for SAS, SATA and
> STP/<native>SATA-SATAII compliant type devices would be the same.
> Amit Shah
> Sr. Design Engr
> -----Original Message-----
> From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of Henry
> Sent: Tuesday, June 15, 2004 10:16 AM
> To: t10 at t10.org
> Subject: Question: OOB - SAS vs STP/SATA detection
> * From the T10 Reflector (t10 at t10.org), posted by:
> * Henry Wong <Henry at scs.agilent.com>
> > Draft Scenarios:
> > A) SAS Rev5 (sec 6.5) draft is more stringent than SATA & SATA-II
> > terms of detection of OOB signaling. SAS draft documents
> > describe detection rqmts of Burst, Idle, & Negation timings.
> > Also indicated is the need that the "...receiver shall
> > detect an OOB signal after.... .....consecutive idle
> > time/burst time pairs...."
> > --> This theme is consistant thru-out the SAS (current/previous)
> > B) The current T13 ATA/ATAPI 7 - Vol3 (sec 14.5.6) draft on SATA
> > that "...OOB signals shall be observed by detection of
> > spacing between adjacent bursts of activity..." "It is not
> > for a receiver to check the duration of an OOB burst."
> > --> This theme is consistant within the ATA/ATAPI7
> (current/previous) docs.
> > C) The SerialATA Rev 1.0a (6.7.4) draft has "...OOB signals shall
> be observed
> > by detection of temporal spacing between adjacent bursts of
> > activity..."
> > --> This draft omits the second sentence that exists in the T13
> > about "...not required... ...to check the duration of an OOB
> > I was unable to find any post Rev 1.0a draft documents that
> > elaborated on OOB signal detection.
> > It appears that there are two types of OOB detection rqmts based on a
> > protocol support. Device can support protocol(s):
> > 1) SAS only (receiver detection based on Burst, Idle, & Negation
> > of idle/burst pairs...see A above).
> > and/or
> > 2) STP/<native>SATA-SATAII compliant type devices (receiver
> detects spacial
> > bursts and depending on draft <T13 vs SerialATA> may ignore
> burst duration)
> > QUESTION <need for clarification/verification>:
> > >>> Is the resultant of these 3 draft docs indicating that devices
> > that support more than SAS only (i.e. SAS+STP, SAS+SATA,
> > SAS+STP+SATAII, & etc, & etc....) will need to implement two types
> > of receiver OOB detection designs ?? For example, on power-up
> > transmit voltage level adjustments <see SAS-r5, section 5.3.4> a
> > that supports attaching to SAS+STP, will detect DC Idles (a.k.a
> > temporal spacing) ignoring burst duration length while
> > at SATA transmit levels and if necessary switches to SAS transmit
> > and then looks for OOBs with idle/burst time pairs that meet the
> > described in Table 40, 41, & 42 <see SAS-r5, section 6.5>.
> > >>> So, bottomline... is it true that all but SAS Only devices will
> > some sort of "dual mode OOB detection scheme" to meet the current
> > draft/standard docs presently available ???
> > We're probably all aware of the various hows/whys (e.g. clock
> > differences, DC Idle generation/detection, & etc.).... but the big
> > question is how well interoperability is between SAS & STP/SATA
> > derivatives).
> > ====> I apologize for the long note... I tried to keep it short. Any
> > comment/clearification would be of great interest... for
> > a) continue & design for dual OOB detection (based on
> SAS ..vs..
> > STP/SATA protocol modes)
> > b) change/re-align the drafts to better co-exist
> > c) clearify my misconceptions from the 3 different
> drafts mentioned
> > above
> > d) ideas/comments ??????
> > Thanks!
> > Best Regards, Henry
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C_O_O_L.......... I guess you meant (Table-39 in SASr5 ..OR..
Table-40 in the current SAS-1.1r4). Looking at them I now see
your point; also, noticed the sentence just before table saying:
"The burst time is not used to distinguish between signals."
Based on what you've pointed out, the table does basically indicate
--> "any amount of time". I focused too much on the paragraph
after Table-42 where the infamous receiver "SHALLs" appear.
Best Regards, Henry
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