Question: OOB - SAS vs STP/SATA detection

Shah, Amit M amit.m.shah at intel.com
Wed Jun 16 14:24:35 PDT 2004


* From the T10 Reflector (t10 at t10.org), posted by:
* "Shah, Amit M" <amit.m.shah at intel.com>
*
Henry,

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
Wong
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
in
>        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)
docs.
>     B) The current T13 ATA/ATAPI 7 - Vol3 (sec 14.5.6) draft on SATA
describes
>        that  "...OOB signals shall be observed by detection of
temporal
>        spacing between adjacent bursts of activity..."  "It is not
required
>        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
version
>        about "...not required...  ...to check the duration of an OOB
burst."
>        I was unable to find any post Rev 1.0a draft documents that
further
>        elaborated on OOB signal detection.
>
> It appears that there are two types of OOB detection rqmts based on a
devices
> protocol support. Device can support protocol(s):
>       1) SAS only (receiver detection based on Burst, Idle, & Negation
timings
>          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+SATAII,
>     SAS+STP+SATAII, & etc, & etc....) will need to implement two types
>     of receiver OOB detection designs ??   For example, on power-up
during
>     transmit voltage level adjustments <see SAS-r5, section 5.3.4> a
device
>     that supports attaching to SAS+STP, will detect DC Idles (a.k.a
>     temporal spacing) ignoring burst duration length while
transmitting
>     at SATA transmit levels and if necessary switches to SAS transmit
levels
>     and then looks for OOBs with idle/burst time pairs that meet the
rqmts
>     described in Table 40, 41, & 42 <see SAS-r5, section 6.5>.
>
> >>> So, bottomline... is it true that all but SAS Only devices will
need
>     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
tolerance
> differences, DC Idle generation/detection, & etc.).... but the big
> question is how well interoperability is between SAS & STP/SATA
(native
> derivatives).
>
> ====> I apologize for the long note... I tried to keep it short.  Any
>            comment/clearification would be of great interest... for
example:
>               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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