Adaptec 6805Q 2270700-R User Manual
Product codes
2270700-R
Appendix A: Introduction to SAS
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90
How Do SAS Devices Communicate?
SAS devices communicate with each other through links. A link is a physical connection
between two phys.
between two phys.
As shown in the following figure, SAS devices contain ports (see
), ports contain phys,
and each phy contains one transmitter and one receiver—one transceiver. A phy can belong to
one port only.
one port only.
What’s a Phy?
Phys are part of the physical communication connection between SAS devices. Each phy
contains a transceiver that sends data back and forth between SAS devices.
contains a transceiver that sends data back and forth between SAS devices.
When a connection is formed between two end devices, a link is established from a phy in one
port to a phy in the other port. As shown in the figure above, a wide port can support multiple
independent links simultaneously.
port to a phy in the other port. As shown in the figure above, a wide port can support multiple
independent links simultaneously.
Phys are internal, within SAS connectors (see
SAS cables physically connect one or more phys on one SAS device to one or more phys on
another SAS device.
another SAS device.
Wide
Port
Port
Wide
Port
Port
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Narrow
Port
Port
Phy
Receiver
Transmitter
Narrow
Port
SAS Device
SAS Device
SAS Device
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Phy
Receiver
Transmitter
Wide
Port
Wide
Port
SAS Device
link