XRT83SL216_06 Datasheet, PDF (24/42 Pages) Exar Corporation – 16-CHANNEL E1 SHORT-HAUL LINE INTERFACE UNIT

XRT83SL216
16-CHANNEL E1 SHORT-HAUL LINE INTERFACE UNIT
REV. 1.0.0
3.0 APPLICATIONS
This applications section describes system considerations along with references to application notes available
for reference where applicable.
3.1 Loopback Diagnostics
The XRT83SL216 supports several loopback modes for diagnostic testing. The following section describes the
local analog loopback, remote loopback, and digital loopback.
3.1.1 Local Analog Loopback
With local analog loopback activated, the transmit output data at TTIP/TRING is internally looped back to the
analog inputs at RTIP/RRING. External inputs at RTIP/RRING are ignored while valid transmit output data
continues to be sent to the line. A simplified block diagram of local analog loopback is shown in Figure 15.
FIGURE 15. SIMPLIFIED BLOCK DIAGRAM OF LOCAL ANALOG LOOPBACK
TCLK
TPOS
TNEG
Encoder
TAOS
JA
Timing
Control
Tx
TTIP
TRING
RCLK
Data and
RPOS
Decoder
JA
Clock
Rx
RNEG
Recovery
RTIP
RRING
NOTE: TAOS takes priority over the transmit input data at TPOS/TNEG.
3.1.2 Remote Loopback
With remote loopback activated, the receive input data at RTIP/RRING is internally looped back to the transmit
output data at TTIP/TRING. The transmit input data at TCLK/TPOS/TNEG are ignored while valid receive
output data continues to be sent to the system. A simplified block diagram of remote loopback is shown in
Figure 16.
FIGURE 16. SIMPLIFIED BLOCK DIAGRAM OF REMOTE LOOPBACK
TCLK
TPOS
TNEG
Encoder
TAOS
JA
Timing
Control
Tx
TTIP
TRING
RCLK
Data and
RPOS
Decoder
JA
Clock
Rx
RNEG
Recovery
RTIP
RRING
NOTE: Remote Loop Back takes priority over TAOS.
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