1.3 Phy layer
C141-C013 41
RCD
SNTT
SNTT
RCD
RCD
RCD
no dword
sync
dword
sync
dword
sync
SNTT
SNTT
SNTT
SNTT
SNTT
SNTT
dword
sync
dword
sync
Phy A Rx/
Phy A Tx/
Phy B Rx
no dword
sync
Not supported
by phy B
Not supported
by phy B
G1 rate
G2 rate
G3 rate
G2 rate
(negotiated rate)
ALIGN(0)s
ALIGN(1)s
Time z: SAS speed negotiation sequence begins
Time
RCD
RCD
RCD
Figure 1.12 SAS speed negotiation sequence (Example 1) If the phy does not obtain dword synchronization during the final speed negotiation window, the SAS speed negotiation sequence fails. Figure 1.13 shows the same speed negotiation sequence as in Figure 1.12 when phy B does not obtain dword synchronization during the final speed negotiation window. If this occurs, the handshake is not complete and the OOB sequence shall be retried starting with COMINIT, forcing the phy to retry the whole reset sequence.
Hot Plug
Timeout delay
Phy A Tx/
Phy B Rx
Phy A Rx/
Phy B Tx
RCD
RCD
RCD
RCD
RCD
RCD
RCD
SNTT
SNTT
SNTT
SNTT
SNTT
SNTT
SNTT
SNTT
dword
sync
dword
sync
dword
sync
dword
sync
dword
sync
no dword
sync
no dword
sync
G1 rate
G2 rate
G3 rate
G2 rate
(negotiated rate)
ALIGN(0)s
ALIGN(1)s
Time z: SAS speed negotiation sequence begins
Time
COMINIT
COMINIT
Figure 1.13 SAS speed negotiation sequence (Example 2)