SAS XL state machine to XL transmitter messages

Elliott, Robert (Server Storage) elliott at
Mon Dec 8 14:15:59 PST 2003

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

> * From the T10 Reflector (t10 at, posted by:
> * Gil Romo <gil.romo at>
> *
> There is a discrepancy between 7.15, XL state machine, and 
> Annex G, Expander device handling of connections.
> In 7.15.5 and 7.15.6, the XL2 and XL3 states repeatedly send 
> Transmit Idle Dword  messages to the XL transmitter until
> the first ECR confirmation is received.
> However, G.2, G.3, G.5, G.6, G.7, and G.12 show that the 
> Phy[X] transmitter continuously sends AIP (NORMAL) during 
> this period.  Note this also occurs with Phy[Y] in G.6 and G.7.
> Will someone involved in this area please review?
> ------------
> Gilbert Romo
> Circuits & Integration
> QLogic Corporation, Aliso Viejo, California
> Office: 949-389-6266
> E-mail: gil.romo at

None of the AIPs are intended to be continuously transferred.  They're
supposed to be sent once every 128 dwords (see - the fastest
allowed is 3 out of every 4 dwords and the slowest (what the receiver
cares about) is 1 every 1 ms (to prevent the Open Timeout timer from

XL1 and the XL transmitter descriptions should be clearer that repeated
Transmit AIP messages result in a mix of mostly idle dwords and an
occasional AIP, not a steady stream of AIPs.

XL2 should continue repeating the AIP (NORMAL) at that interval, rather
than just send idle dwords.

XL3 is already scheduled for cleanup regarding AIP (WAITING ON DEVICE)
(so only one gets sent by this expander before it starts forwarding
dwords).  If there is any time gap in XL3 before the first AIP (WAITING
ON DEVICE) is transmitted, the previous AIP should be repeated every 128
dwords while the XL state machine waits.

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

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