Serial Storage Architecture

[SSA Bus Description]
[SSA Standard Organizations] [SSA OnLine Specifications]

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.
Refer to the note on the obsolescence of this interface.

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Editor note; I have the impression this bus is OBSOLETE, being defined at TTL levels.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.
It would be basically impossible for this standard to continue to compete with newer standards while relying on TTL signaling rates.
The pinout for a six pin internal port is shown below.

Internal Port PinOut
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
It doesn't appear that this standard was every released by the IEEE.

{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.
Which would imply that these standards describe an Out-dated or legacy Interface.
Normally when a specification is not re-affirmed means that interest in the standard has faded.

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; Basically a list of semiconductor vendors and other companies producing products

{SSA Bus Index}

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Modified: 3/04/12
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