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.
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, 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. <<GP
- Added in a more realistic segment compination were problems occur into
the e.g list in this paragraph.>>
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).
<<GP - The term 'legacy SAS' should be
removed. The sentence should be stated as 'These
high-loss TxRx connections may not be suitable for versions of SAS that
comply with prior versions of this standard or 6 Gbps SATA devices.' and
the last sentence should be deleted as it does not give the reader any
useful information. >>