XRT79L71
PRELIMINARY
369
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
5.3.1.8
The HDB3 Decoder Block
The purpose of the HDB3 Decoder block is to decode the "inbound" E3 traffic from the "HDB3 Line Code", into
a digital data-stream. In the case of the XRT79L71, the HDB3 Decoder block will always be enabled and the
user has no ability to disable the HDB3 Decoder block.
5.3.1.9
Performance Characteristics of the Receive E3 LIU Block
These next few sections will present the performance characteristics of the Receive DS3/E3 LIU Block, within
the XRT79L71. In particular these sections will address the following parameters for E3 Applications.
Receive Sensitivity
Interference Margin
Jitter Tolerance
5.3.1.9.1
Receive Sensitivity Capability of the Receive E3 LIU Block
For DS3 Applications, the Receive E3 LIU Block MUST be capable of receiving a "E3" signal that has been
attenuated by anywhere from 0 to 12dB of cable loss, and at least 6dB of flat loss, in a un-erred manner.
Table 45 summarizes the Receive Sensitivity of the Receive DS3/E3 LIU Block, within the XRT79L71.
Test Approach
The Adtech AX-4000 tester was configured to generate ATM cells and to map these ATM cells into an E3 data
stream, which was then to be output as a bipolar line signal.
The E3 line signal was then routed to the ME-1005 75W Coaxial Cable Simulator (from Mountain Engineering).
The Cable Simulator was configured to insert the "user-selected" amount of "shaped" (or cable) loss into this
E3 line signal.
After this E3 line signal has been subjected to an appropriate amount of flat-loss and cable loss, it was then
routed to the Receive Input of the XRT79L71 Evaluation Board.
The XRT79L71 Evaluation Board was
configured to operate in the "UTOPIA Loop-back" Mode. Therefore, the XRT79L71 Evaluation Board would
handle the attenuated E3 line signals in the following manner.
The Receive DS3/E3 LIU Block (within the XRT79L71) would receive this E3 line signal and perform "Clock"
and "Data" Recovery on this line signal.
This "Recovered" Clock and Data would then be routed to the Receive DS3/E3 Framer block, the Receive
ATM Cell Processor and the Receive UTOPIA Interface block. The UTOPIA FPGA would then read out the
contents of these ATM cells and it would then write these ATM cells back into the Transmit UTOPIA Interface
block.
FIGURE 171. ILLUSTRATION OF TEST SET-UP TO PERFORM THE "RECEIVE SENSITIVITY LOW-LEVEL" TEST
Adtech
AX-4000
Tester
Adtech
AX-4000
Tester
Flat Loss
Attenuator
Flat Loss
Attenuator
Cable
Simulator
Cable
Simulator
XRT79L71
Evaluation
Board
XRT79L71
Evaluation
Board