Wording for TxRx connection section

Alvin.Cox at seagate.com Alvin.Cox at seagate.com
Wed Nov 14 11:42:53 PST 2007


Attachment #1: <A HREF="r0711142_nameless-2328-2-1.html">nameless-2328-2-1.html</A>

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 at 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 10
15 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).



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