XRT83SL28
xr
8-CHANNEL E1 SHORT-HAUL LINE INTERFACE UNIT
REV. 1.0.0
1.0 RECEIVE PATH LINE INTERFACE
The receive path of the XRT83SL28 LIU consists of 8 independent E1 receivers. The following section
describes the complete receive path from RTIP/RRING inputs to RCLK/RPOS/RNEG outputs. A simplified
block diagram of the receive path is shown in Figure 4.
FIGURE 4. SIMPLIFIED BLOCK DIAGRAM OF THE RECEIVE PATH LINE TERMINATION (RTIP/RRING)
RCLK
RPOS
RNEG
RTIP
HDB3
Decoder
Rx Jitter
Attenuator
Clock & Data
Recovery
Peak Detector
& Slicer
RRING
1.1
Internal Termination
The input stage of the receive path accepts standard E1 coaxial cable or E1 twisted pair inputs through RTIP
and RRING. The physical interface is optimized by placing the terminating impedance inside the LIU. This
allows one bill of materials for all modes of operation reducing the number of external components necessary
in system design. The receive termination impedance is selected by programming TERSEL[1:0] to match the
line impedance. The XRT83SL28 has the ability to switch the internal termination to "High" impedance for
redundancy applications. See Redundancy in the Applications Section of this datasheet. Selecting the internal
impedance is shown in Table 1. A typical connection diagram is shown in Figure 5.
TABLE 1: SELECTING THE INTERNAL IMPEDANCE
TERSEL[1:0]
0h (00)
RECEIVE TERMINATION
75Ω for Tx and "High-Z" for Rx
120Ω for Tx and "High-Z" for Rx
75Ω for Tx and Rx
1h (01)
2h (10)
3h (11)
120Ω for Tx and Rx
FIGURE 5. TYPICAL CONNECTION DIAGRAM USING INTERNAL TERMINATION
XRT83SL28 LIU
RTIP
1:1
Receiver
Input
Line Interface E1
RRING
One Bill of Materials
Internal Impedance
14
EXAR [ EXAR CORPORATION ]
