Query on detection of triple and redundant primtive sequences

Gerry.Houlder at seagate.com Gerry.Houlder at seagate.com
Wed Feb 27 08:33:55 PST 2008

* From the T10 Reflector (t10 at t10.org), posted by:
* Gerry.Houlder at seagate.com
A point to remember for either case is that deletable primitives (e.g.,
ALIGN) are intended to be either removed from the data stream or ignored
(i.e., treated as if they weren't there). Other things, like idle dwords or
invalid dwords, are not removed or ignored before detecting primitives.
Triple primitive sequences are transmitted 3 in a row and must be detected
3 in a row to be detected. This is a very strict detection case where any
invalid dword or disparity error in any of the three primitives would cause
the sequence to not be recognized.
Redundant primitive sequences are transmitted 6 in a row but only 3 in a
row is needed to detect the primitive sequence. This allows for any one of
the 6 primitives to be corrupted (e.g., disparity error) and the receiver
can still detect the primitive sequence.
In summary, the difference between these cases is triple primitive
sequences are not tolerant of disparity or other invalid dword type errors
but redundant primitive sequences provide for some tolerance of bit errors.
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				       Query on detection of triple and    
				       redundant primtive sequences	   
	     02/27/2008 06:47						   
I have a query on detection of triple and redundant primtive sequences.
As per Specifications T10/1760-D Revision 11,
For Triple Primitive sequences,
Receivers shall detect a triple primitive sequence after the identical
primitive is received in three consecutive
For Redundant Primitive sequences,
A receiver shall detect a redundant primitive sequence after the identical
primitive is received in any three of
six consecutive dwords.
Also it is mentioned that,
Any number of deletable primitives may be sent inside primitive sequences
without affecting the count or
breaking the consecutiveness requirements.
Now, if we receive a sequence like this:
RP, A, A, RP, A, A, RP, A, A, RP, RP, RP
where (RP = Redundant primitive, A =  Align)
then will RP be detected? If yes, then :
1. it will imply the same logic of detection for redundant and triple
primitive sequences.
2. what is the use of sending triple primitives thrice and redundant
primtives six times if both
    are detected on reception of three identical primitives?
Pooja Gupta
Accelerating designs
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