Redundant primitive sequences

Elliott, Robert (Server Storage) Elliott at
Tue Feb 28 11:29:31 PST 2006

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The figure is showing when the receiver detects the primitive sequence
under a variety of different scenarios (but not every possible
scenario). If a transmitter sends more than 6, they'll still just be
decoded as part of one primitive sequence.
There are so few redundant primitives - BREAK, BROADCAST, and HARD_RESET
- that some of the details are not important.  After HARD_RESET, nothing
else matters.  After BREAK, another BREAK has no effect.  Identical
BROADCASTs are already subject to being combined by expanders, so
whether you decode 1 or two makes no difference.
If you're testing a transmitter, I'd flag it as a bug if it sent more
than 6 because there is no benefit from doing so and it was probably not
intended by the designer.  In a real system, though, receivers won't
Rob Elliott, elliott at 
Hewlett-Packard Industry Standard Server Storage Advanced Technology 
  From: Yamini [mailto:Yamini at] 
  Sent: Tuesday, February 07, 2006 10:40 PM
  To: t10 at; Elliott, Robert (Server Storage)
  Subject: Redundant primitive sequences
  I have a question about Primitive Sequences. The number of
primitives that a sender can send in a Redundant Primitive Sequence is
not clearly mentioned in the spec. I hope someone from the reflector can
clarify this for me.
  'Figure 131 - redundant primitive sequence' in  SAS spec
2.0(sas2r00.pdf) shows 10 back to back Primitives in a redundant
sequence. Is this legal?
  The reason why ask is that the text preceeding this figure says:
  " Redundant primitive sequence
  Primitives that form redundant primitive sequences (e.g.,
BROADCAST (CHANGE)) shall be sent six times consecutively. ALIGNs and
NOTIFYs may be sent inside primitive sequences as described in 
  A receiver shall detect a redundant primitive sequence after the
identical primitive is received in three 
  consecutive dwords. After receiving a redundant primitive
sequence, a receiver shall not detect a second instance of the same
redundant primitive sequence until it has received six consecutive
dwords that are not 
  any of the following: 
  a) the original primitive; or 
  b) an ALIGN or NOTIFY." 
  I interpret it as the sender SHALL only send six consecutive
primitives. So is sending more than 6 primitives in a redundant sequence
an error? Also, is sending sequences without a six dword gap in between
sequences legal? The above section from the spec states clearly about
the receiver's requirements but not the sender's side. 
  Thanks in advance, 

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