I have made some changes to the woding of this section to help implementation and interpretation of cable/backplane specs. Please review and provide discussion on the reflector or during tomorrow's call.

Alvin Cox
Seagate Technology, LLC
Office 405-381-8067
Cell 405-206-4809
E-Mail  alvin.cox@seagate.com

5.3.3.2 TxRx connection characteristics

TxRx connection overview

Each TxRx connection shall support a bit error ratio (BER) that is less than 10^-12 (i.e., fewer than one bit error per 10¹² bits). The parameters specified in this standard support meeting this requirement under all conditions including the minimum input and output amplitude levels.

A TxRx connection may be constructed from multiple TxRx connection segments (e.g., backplane, cable, backplane). In such cases, the individual TxRx connection segment should have loss characteristics less than the total TxRx connection loss characteristic allowed for the application. Specifying the loss characteristics for individual TxRx connection segments is the responsibility of the implementer and is beyond the scope of this specification.
       
Each TxRx connection segment shall comply with the impedance requirements detailed in 5.2.6 for the conductive material from which they are formed. An equalizer network, if present, shall be considered part of the TxRx connection.

TxRx connections shall be applied only to homogenous ground applications (e.g., between devices within an enclosure or rack, or between enclosures interconnected by a common ground return or ground plane).

5.3.3.2.1 1.5 and 3 Gbps applications

Each TxRx connection shall be designed such that its loss characteristics are less than:

a) the loss of the TCTF test load plus ISI at 3 Gbps (see figure 108 in 5.3.2.3) over the frequency range of 50 MHz to 3 000 MHz; or
b) the loss of the low-loss TCTF test load plus ISI at 3 Gbps (see figure 110 in 5.3.2.4) over the frequency range of 50 MHz to 3 000 MHz, if the system supports SATA devices using Gen2i levels (see SATA-2) but the receiver device does not support SATA Gen2i levels through the TCTF test load.

Each TxRx connection shall meet the delivered signal specifications in table 58 (see 5.3.7.2).

For external cable assemblies, these electrical requirements are consistent with using good quality passive cable assemblies constructed with shielded twinaxial cable with 24 gauge solid wire up to 6 meters in length if no other TxRx connection segments are included in the TxRx connection.

5.3.3.2.2  6 Gbps applications

For 6 Gbps applications, the TxRx connection shall support a bit error ratio (BER) that is less than 10^-15 (i.e., fewer than one bit error per 10¹⁵ bits) based on digital communication link simulation results, with data input from S-parameter measurements of the TxRx connection, the specified reference transmitter device, and the specified reference receiver device. Figure 105 illustrates an example circuit for simulation. The specific simulation program used is beyond the scope of this specification. Simulations typically do not include all aspects of noise that may degrade the received signal quality. The support of a BER that is less than 10^-15 by simulation should yield an actual BER that is less than 10^-12. For external Mini SAS 4x cable assemblies, these electrical requirements are consistent with using good quality passive cable assemblies constructed with shielded twinaxial cable with 24 gauge solid wire up to 10 meters in length if no other TxRx connection segments are included in the TxRx connection..

SAS 6 Gbps transceiver devices incorporate enhanced features to allow them to operate over high-loss TxRx connections. These high-loss TxRx connections may not be suitable for legacy SAS or 6 Gbps SATA devices. Care should be used to determine if a SAS device location supports a legacy SAS or 6 Gbps SATA device (see SATA).