Small Computer Systems Interface
[Serial SCSI Description] [SAS Interface ICs]
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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 switching.
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 | 1 Physical | 2 Physical | 3 Physical | 4 Physical |
---|---|---|---|---|
name | Link | Links | Links | Links |
Rx 0+ | S1 | S1 | S1 | S1 |
Rx 0- | S2 | S2 | S2 | S2 |
Rx 1+ | N/A | S3 | S3 | S3 |
Rx 1- | N/A | S4 | S4 | S4 |
Rx 2+ | N/A | N/A | S5 | S5 |
Rx 2- | N/A | N/A | S6 | S6 |
Rx 3+ | N/A | N/A | N/A | S7 |
Rx 3- | N/A | N/A | N/A | S8 |
Tx 3- | N/A | N/A | N/A | S9 |
Tx 3+ | N/A | N/A | N/A | S10 |
Tx 2- | N/A | N/A | S11 | S11 |
Tx 2+ | N/A | N/A | S12 | S12 |
Tx 1- | N/A | S13 | S13 | S13 |
Tx 1+ | N/A | S14 | S14 | S14 |
Tx 0- | S15 | S15 | S15 | S15 |
Tx 0+ | S16 | S16 | S16 | S16 |
Signal Ground | G1 - G9 | G1 - G9 | G1 - G9 | G1 - G9 |
Chassis Ground | Housing | Housing | Housing | Housing |
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}
T10 SCSI Documents, Specifications and Reference Info [www.t10.org]
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
SCSI components might cover the physical portion [phy], or the protocol portion of the standard.
The physical or really the electrical portion would also be identical to the SATA specification, because they share that portion.
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}
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Modified 6/13/15
Copyright © 1998 - 2016 All rights reserved Larry Davis