LSI SAS6160 manual SAS Phys, Ports, and Connectors, Link between Two Single SAS Phys

LSISAS6160 SAS Switch User Guide Chapter 1: Overview SAS Phys, Ports, and Connectors

1.3SAS 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.

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.

Phy			Phy
Transceiver			Transceiver
	TX-		Receiver
Transmitter	TX+
		RX-
Receiver		RX+	Transmitter

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.

LSI Corporation September 2010 Page 9