Small Computer Systems Interface
[Serial SCSI Description] [SAS Interface ICs]
[SAS Standard Organizations]
[Home]
The Serial Attached SCSI [SAS] Bus defines Physical layer, PHY Layer, Link Layer, Port layer, and Application Layer. SAS may also just be called Serial SCSI. The Physical Layer consists of two sets of differential lines, one receive set and one transmit set [4-wire total]. The PHY Layer connects the differential Transmitter and Receiver circuits [ICs] to the Physical Layer, which defines the cable, connector, and transceiver [Transmitter / Receiver] characteristics. The external connector will accept 4 physical links, while the cable may hold between 1 and 4 physical links. Internal connectors are also defined. Two data rates are defined: 1.5Gbps and 3.0Gbps over a 100 ohm [+ 15 ohm] differential impedance cable. SAS uses the Serial ATA physical interface, including the connector receptacle and connector plugs. SAS transmits data using 8B/10B at a maximum level of 1.2 volts [Tx voltage = 800-1600mV], [Rx voltage = 275-1600mV]. SAS uses big-endian, while SATA uses little-endian byte ordering. SAS uses a 32 bit CRC. Like SATA, SAS uses LVDS
Two types of ports are defined: A Narrow Port which communicates
over a narrow link and contains only one transmit/receive pair, and
Wide Port which communicates over a Wide link and contains more
than one transmit/receive pair. The Port reside in the
PHY layer, and the Link resides in the Physical
layer
The Serial Attached SCSI - 2 (SAS-2) draft standard is the second generation of SAS, which adds an option for a 6 Gb/sec link speed. It is based upon SAS-1.1. It continues to document both a physical Layer that is compatible with Serial ATA and protocols for transporting SCSI commands to SAS devices and for transporting ATA commands to SATA devices. Refer to this page link for the Parallel SCSI bus description [older interface].
| Signal |
|
|
|
|
|---|---|---|---|---|
| Name |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Serial Attached SCSI [SAS] uses three transport protocols:
... 1; Serial SCSI Protocol [SSP] which maps in SCSI,
supporting multiple initiators and targets
... 2; Serial ATA Tunneled Protocol [STP] mapping Serial
ATA, supporting multiple initiators and targets
... 3; Serial Management Protocol [SMP] a management
protocol.
Serial SCSI is used as the physical interface for computer Hard Disk
Drives [HDD].
SCSI Standards List {ANSI}
SCSI Documents, Specifications and Reference Info {T10}
Serial Attached SCSI - {SAS), 07/2003, released date
Serial Attached SCSI - 1.1 {SAS-1.1), 09/2005, released date
Serial Attached SCSI - 2.0 {SAS-2.0), 11/2007, released date
LSI Corporation {SAS Interface IC}
Silicon Bridge {SATA/SAS PHY Interface IC}
Vitesse {Serial Attached SCSI Phy Interface IC}
Select the COMPONENTS icon below for additional types of Integrated Circuit manufacturers.
{Back to Serial SCSI Bus Index}
Engineering Key words: Serial Attached SCSI Standard, SAS, Hard Drive Bus, Small Computer System Interface Standard, SCSI Specification, SSA Spec, Ultra SCSI Personal Computer Interface, IC, SCSI Physical Interface, Description, Pinout, Parallel SCSI, Direct Attached Storage [DAS], Networked Attached Storage [NAS], Storage Area Network [SAN].
|
|
|||||||
| Home | |||||||
|
|
|||||||
|
|
|
|
|
|
|
|
|
| Distributors | Components | Equipment | Software | Standards | Buses | Design | Reference |