XRT83SL216IB View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT83SL216IB' PDF : 41 Pages View PDF
XRT83SL216
REV. 1.0.0
16-CHANNEL E1 SHORT-HAUL LINE INTERFACE UNIT
3.1.3 Digital Loopback
With digital loopback activated, the transmit input data at TCLK/TPOS/TNEG is looped back to the receive
output data at RCLK/RPOS/RNEG. The receive input data at RTIP/RRING is ignored while valid transmit
output data continues to be sent to the line. A simplified block diagram of digital loopback is shown in
Figure 17.
FIGURE 17. SIMPLIFIED BLOCK DIAGRAM OF DIGITAL LOOPBACK
TCLK
TPOS
TNEG
Encoder
JA
TAOS
Timing
Control
Tx
TTIP
TRING
RCLK
Data and
RPOS
Decoder
JA
Clock
Rx
RNEG
Recovery
RTIP
RRING
3.2 Interfacing the Transmit Section of the XRT83L216 to the Line
ITU-T G.703 specifies that the E1 line signal can be transmitted over coaxial cable and terminated with 75Ω or
transmitted over twisted-pair and terminated with 120Ω.
In both applications (e.g., 75Ω or 120Ω, the user is advised to interface the Transmitter to the Line, in the man-
ner as depicted in Figure 18 and Figure 19, respectively.
FIGURE 18. INTERFACING THE XRT83L216 TO THE LINE FOR 75Ω APPLICATIONS (1 CHANNEL SHOWN)
75 Ω Coax
75 Ω
Signal
Source
75 Ω Coax
R Load
75 Ω
2 :1
2:1
RTIP
18.7 Ω
Rx Input
RRING
9.1 Ω
9.1 Ω
TTIP
Tx Output
TRING
RPOS/RData
RNEG/LCV
RClk
+3.3 V
RVDD
TVDD
AVDD
0.1 µF
0.1 µF
0.1 µF
10µF
TGND
AGND
TNEG/CODE
TPOS/TData
TClk
Ferrite
Bead
23
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