LSI SAS6160 - Manual (Page 9)

LSI Corporation | September 2010 Page 9
LSISAS6160 SAS Switch User Guide Chapter 1: Overview | SAS Phys, Ports, and Connectors
„ Flash Memory – Each LSISA2x36 expander connects to a parallel flash through the
expander’s external memory interface. This flash is used for firmware storage and
execution, as well as nonvolatile data such as Ethernet MAC address and SAS WWID.
„ PBSRAM Memory – The PBSRAM is attached to each expander’s external memory
interface, and is used for the capture buffer, run-time stack, and heap, along with
miscellaneous items.
„ Dual Port Memory – This dual port SRAM provides shared memory space between
the master and slave expanders.
„ Temperature Sensors – The temperature sensors are inputs that control the speed
of the fans.
1.3 SAS Phys, Ports, and
Connectors
Phys and ports are a basic concept of SAS. A phy is the basic physical connection point
for a SAS device. A phy contains a single transmitter and receiver, which communicate
across a SAS link to a single transmitter and receiver in another phy, as the following
figure illustrates.
Figure 4: Link between Two Single SAS Phys
Each single-phy link (also called a narrow port) supports a maximum bandwidth of
600 MB/s (6Gb/s) per direction, with a total bandwidth of 1200 MB/s full duplex in both
directions.
A SAS wide port consists of more than one SAS phy (an 8-phy SAS port is also possible)
that transmit and receive data by using the same SAS address when connected to
another SAS wide port. In other words, the port is created dynamically when the
connection is made. The following figure shows both a narrow port and a wide port.
Transmitter
Transmitter
Receiver
Receiver
RX-
RX+
TX-
TX+
Transceiver Transceiver
Phy Phy