Completion of TRAIN or TRAIN_DONE sequences

Geoff Hibbert geoff.hibbert at
Tue Feb 19 18:25:23 PST 2008

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Hello all,
I have a question regarding a possible ambiguity in the SAS-2 spec at
It says:
"If the phy's receiver is trained and acquires dword synchronization
before TLT, then the phy shall stop transmitting TRAIN patterns and
start transmitting TRAIN_DONE patterns."
It also says that upon transmitting 4 or more TRAIN_DONE patterns and
receiving the minimum 1 TRAIN_DONE before MTT,
"then the phy shall:
a)	 stop transmitting TRAIN_DONE patterns;
b)	 start transmitting dwords from the link layer; and
c)	 consider the Train-SNW to be valid."
When it says "stop transmitting" is the intention that TRAIN and
TRAIN_DONE patterns always be sent in their entirety (primitive sequence
followed by 58 scrambled dwords) before switching to the next item, or
may the phy interrupt whatever TRAIN/TRAIN_DONE sequence it is in the
middle of transmitting to switch to transmitting the next item?
-Geoff Hibbert
-Finisar Corporation

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