XRT83L314 Datasheet, PDF (38/84 Pages) Exar Corporation – 14-CHANNEL T1/E1/J1 LONG-HAUL/SHORT-HAUL LINE INTERFACE UNIT

XRT83L314
14-CHANNEL T1/E1/J1 LONG-HAUL/SHORT-HAUL LINE INTERFACE UNIT
REV. 1.0.0
4.0 T1/E1 APPLICATIONS
This applications section describes common T1/E1 system considerations along with references to application
notes available for reference where applicable.
4.1 Loopback Diagnostics
The XRT83L314 supports several loopback modes for diagnostic testing. The following section describes the
local analog loopback, remote loopback, digital loopback, and dual loopback modes.
4.1.1 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 31.
FIGURE 31. SIMPLIFIED BLOCK DIAGRAM OF LOCAL ANALOG LOOPBACK
TCLK
TPOS
TNEG
NLC/PRBS/QRSS
Encoder
JA
TAOS
Timing
Control
Tx
RCLK
Data and
RPOS
Decoder
JA
Clock
Rx
RNEG
Recovery
TTIP
TRING
RTIP
RRING
NOTE: The transmit diagnostic features such as TAOS, NLC generation, and QRSS take priority over the transmit input
data at TCLK/TPOS/TNEG.
4.1.2 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 remote loopback includes the Receive JA (if enabled). 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 32.
FIGURE 32. SIMPLIFIED BLOCK DIAGRAM OF REMOTE LOOPBACK
NLC/PRBS/QRSS
TAOS
TCLK
TPOS
TNEG
Encoder
JA
Timing
Control
Tx
RCLK
Data and
RPOS
Decoder
JA
Clock
Rx
RNEG
Recovery
TTIP
TRING
RTIP
RRING
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