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SAS Interface
28 C141-C013
1.1.6 Connections
A connection is a temporary association between a SAS INIT port and a SAS
TARG port. During a connection all dwords from the SAS INIT port are
forwarded to the SAS TARG port, and all dwords from the SAS TARG port are
forwarded to the SAS INIT port.
A connection is pending when an OPEN address frame has been delivered along a
completed pathway to the destination phy but the destination phy has not yet
responded to the connection request. A connection is established when an
OPEN_ACCEPT is returned to the source phy.
A connection enables communication for one protocol: SSP, STP, or SMP. For
SSP and STP, connections may be opened and closed multiple times during the
processing of a command.
The connection rate is the effective rate of dwords through the pathway between a
SAS INIT phy and a SAS TARG phy, established through the connection request.
Every phy shall support a 1,5 Gbps connection rate regardless of its physical link
rate.
One connection may be active on a physical link at a time. If the connection is an
SSP or SMP connection and there are no dwords to transmit associated with that
connection, idle dwords are transmitted.
The number of connections established by a SAS port shall not exceed the number
of SAS phys within the SAS port (i.e., only one connection per SAS phy is
allowed). There shall be a separate connection on each physical link.
If multiple potential pathways exist between the SAS INIT port(s) and the SAS
TARG port(s), multiple connections may be established by a SAS port between
the following:
a) one SAS INIT port to multiple SAS TARG ports;
b) one SAS TARG port to multiple SAS INIT ports; or
c) one SAS INIT port to one SAS TARG port.
Once a connection is established, the pathway used for that connection shall not
be changed (i.e., all the physical links that make up the pathway remain dedicated
to the connection until it is closed).