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SAS Interface
42 C141-C013
1.3.6.1 Phy reset sequence after devices are attached
Since SAS signal cable connector does not include power lines, it is not possible
to detect the physical insertion of the signal cable connector onto a plug. Non-
cabled environments may similarly not have a way to detect physical insertion of
a device. As a result, every time a phy reset sequence is originated:
Figure 1.14 shows how two phys complete the phy reset sequence if the phys are
not attached at power on. In this example, phy A and phy B are attached some
time before phy B's second hot-plug timeout occurs. Phy B's OOB detection
circuitry detects a COMINIT after the attachment, and therefore phy B transmits
COMSAS, since it has both transmitted and received a COMINIT. Upon
receiving COMSAS, phy A transmits its own COMSAS. The SAS speed
negotiation sequence follows.
A
Phy A Tx
COMINIT
COMINIT
COMINIT
COMSAS
Hot-Plug
Timeout
Hot-Plug
Timeout
Phy A Rx
B
Time=0
Time=y
COMSAS
Time=z
Incomplete
COMINIT
COMSAS
COMSAS
COMINIT
COMINIT
COMINIT
Time=0
Time=y
Time=z
Phy B Tx
A
B
Hot-Plug
Timeout
Phy B Rx
A: SAS phy A power on
B: SAS phy B power on
Time y : SAS phy A attached to SAS phy B
Time z: SAS phy A and SAS phy B start the SAS speed negotiation sequence
Figure 1.14 Phy reset sequence (Example)