SSA Bus Description, Serial Storage Architecture pinout

SSA Bus

Serial Storage Architecture

[SSA Bus Description]
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Serial Storage Architecture [SSA] Bus Description

Serial Storage Architecture [SSA] Bus defines the Physical layer interface.
Additional documents describe other layers, SSA may be used with SCSI protocols [SCSI-2 and/or SCSI-3].

Data transmission is 20MBps at up to 40 meters, with full duplex operation up to 40MB/s [20MBps in each direction].
A maximum distance of 2.5 kilometers is possible, but only at a rate of 5MBps.
SSA uses standard [5 volt] TTL switching levels [The differential voltage is 200mV].
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 1 to 2 physical links.

A character is defined as 10 bits. The Bit Encoding used is: Non Return to Zero (NRZ) encoding for data communication on a differential two wire bus. The use of NRZ encoding ensures compact messages with a minimum number of transitions and high resilience to external disturbance. Lines are terminated to 3.3 volts [2.97 minimum / 3.63 maximum] via a 75 ohm resistor.
The differential cable impedance is 150 ohms. The internal connector pin-out is shown below, other connector pinouts are also defined. In addition a Power connector is defined.

Editor note; I have the impression this bus is OBSOLETE, being defined at TTL levels. How ever, it may still reside on a few IBM main-frames. The pinout for a six pin internal port is shown below.

**Internal Port PinOut**
Pin	Signal Name
1	LineOut+
2	LineOut-
3	Chassis/Power GND
4	Logic GND
5	LineIn+
6	LineIn+

{SSA Bus Index}

SSA Standard Organizations

ANSI; SSA Standards List
T10; SSA Documents, Specifications and Reference Info

{SSA Interface Index}

SSA Standard

Serial Storage Architecture - Physical Layer 1 (SSA-PH1) Rev 9c 1996
Serial Storage Architecture - Physical Layer 2 (SSA-PH2) Rev 5b 1997
Serial Storage Architecture - SCSI-3 Protocol (SSA-S3P) Rev 5b 1997
Serial Storage Architecture - Transport Layer 2 (SSA-TL2) Rev 5b 1997

It appears that this specification has not been re-affirmed yet. So the release dates listed above for the standards appear to be current.

There are no companies that have been identified that produce components for the SSA interface.
However this site does include a generic listing of manufacturers;
Refer to Component Manufacturers, ordered by name.

{Back to SSA Bus Index}

Engineering Design Key words: SSA Standard, SAS, Serial Storage Architecture Hard Drive Bus, Small Computer System Interface, SCSI Specification, SSA Spec, Ultra SCSI Personal Computer Interface, IC, SCSI III Physical Interface, Description, Pinout, Pin-Out, Signal Names, Mainframes, LAN servers, Direct Attached Storage [DAS], Networked Attached Storage [NAS], Storage Area Network [SAN], legacy Interface, Out-dated.


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