SAS Phy layer _ some queries

Jim Lott Jim.Lott at
Thu Sep 2 08:44:45 PDT 2004

* From the T10 Reflector (t10 at, posted by:
* Jim Lott <Jim.Lott at>

SAS1.1r5 section 6.5, with regard to oob states:

"A receiver shall detect an OOB signal after receiving four consecutive idle
time/burst time pairs (see figure 58). It is not an error to receive more
than four idle time/burst time pairs. A receiver shall not detect the same
OOB signal again until it has detected the corresponding negation time
(i.e., a COMINIT negation time for a COMINIT) or has detected a different
OOB signal (e.g., if a COMINIT was previously detected, then four sets of
COMWAKE idle times followed by burst times are detected, a COMWAKE is
detected; another COMINIT
may follow)."


Let's assume that as many as 100 COMINIT burst idle pairs are received
without the negation at the end.  The burst idle pairs are changed to an
invalid OOB or a different OOB signal at some point within the 100 pair.
COMINIT detected is sent to the SP state machine after 4 consecutive valid
pairs are received.


What happens after the invalid sequence (or a different OOB signal) is

The COMINIT  has been detected and the OOB sequence changes to COMWAKE.  

Does the COMINIT detected remain valid?  

Should COMWAKE detected become valid after detecting 4 COMWAKE sequences?  

Should the COMINIT be considered completed upon detection of the COMWAKES or
the fact that valid COMINITs are no longer being received?


-----Original Message-----
From: owner-t10 at [mailto:owner-t10 at] On Behalf Of Elliott,
Robert (Server Storage)
Sent: Thursday, August 26, 2004 1:51 PM
To: t10 at
Subject: RE: SAS Phy layer _ some queries

* From the T10 Reflector (t10 at, posted by:
* "Elliott, Robert (Server Storage)" <elliott at>

> -----Original Message-----
> From: owner-t10 at [mailto:owner-t10 at] On Behalf Of Mona
> Sent: Monday, August 23, 2004 6:44 AM
> To: t10 at
> Subject: SAS Phy layer _ some queries
> * From the T10 Reflector (t10 at, posted by:
> * Mona <monika.talwar at>
> *
> I am studying SAS1.1 specifications.
>  I have some queries related to the SAS specifications
>  -- For how much time shall state machine wait for some transmitted
>   messages from transmitter, for example COMSAS transmitted?

That is design-specific. The "Transmitted" signals are conceptual signals
for the purpose of the standard between an independent state machine and an
independent transmitter.  They might not really exist in hardware. 

>  --Will receiver be able to detect the "completion" of
> detected OOB signal without detecting negation time(6.5)?

It's not supposed to.  If the negation time is not present, then it is not a
completely valid OOB signal.  The "Detected" messages are triggered but not
the "Completed" messages.

>  --"Address frames shall not be terminated early". What's
> meant by early termination??(7.8.1)

Sending less than 7 dwords before the CRC (i.e. 8 dwords before the EOAF).
For example, skipping the last dword of an IDENTIFY because it's "reserved"
is not allowed.

It's also inadvisable to start sending a BREAK while in the middle of
sending an address frame.

>  -- On page 27 (4.1.2) it is stated that SAS phy may use different
>  roles(initiator or target)  in different connections. On 
> page 119(6.6.5) it 
>  is stated that SAS target phys should not originate a new 
> phy reset sequence 
>  after their first attempt. How is target/initiator device 
> exepected to 
> behave  if its first attemt of phy reset sequence fails?

If it has initiator things to do (i.e. wants to discover targets to send
them commands), then it should keep rerunning the phy reset sequence to
search for something newly attached.

If it has no initiator things to do (e.g. it is a tape drive with an
EXTENDED COPY copy manager, which can act as an initiator after being given
some work to do, but it has no such work pending) then it should follow the
target advice and let whatever it is attached to discover it first.  

> Mona
> nSys
> Solutions for emerging standards

Rob Elliott, elliott at
Hewlett-Packard Industry Standard Server Storage Advanced Technology

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