XRT91L32IQ-F View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT91L32IQ-F' PDF : 37 Pages View PDF
XRT91L32
STS-12/STM-4 OR STS-3/STM-1 SONET/SDH TRANSCEIVER
xr
REV. 1.0.2
4.0 DIAGNOSTIC FEATURES
4.1 Serial Remote Loopback
The serial remote loopback function is activated by setting RLOOPS "High". When serial remote loopback is
activated, the high-speed serial receive data from RXIP/N is presented at the high speed transmit output
TXOP/N, and the high-speed recovered clock is selected and presented to the high-speed transmit clock input
of the Retimer. During serial remote loopback, the high-speed receive data (RXIP/N) is also converted to
parallel data and presented at the low-speed receive parallel interface RXDO[7:0]. The recovered receive clock
is also divided by 8 and presented at the low-speed clock output RXPCLKO to synchronize the transfer of the
8-bit received parallel data. A simplified block diagram of serial remote loopback is shown in Figure 16.
FIGURE 16. SERIAL REMOTE LOOPBACK
Serial Remote Loopback
PISO
Re-Timer
LVPECL
Output Drivers
TX Serial Output
RX Parallel Output
SIPO
CDR
LVPECL
Input Drivers
RX Serial Input
4.2 Digital Local Loopback
The digital local loopback is activated when the DLOOP signal is set "High." When digital local loopback is
activated, the high-speed data from the output of the parallel to serial converter is looped back and presented
to the high-speed input of the receiver serial to parallel converter. The CMU output is also looped back to the
receive section and is used to synchronize the transfer of the data through the receiver. In Digital loopback
mode, the transmit data from the transmit parallel interface TXDI[7:0] is serialized and presented to the high-
speed transmit output TXOP/N using the high-speed 622.08/155.52 MHz transmit clock generated from the
clock multiplier unit and presented to the input of the Retimer and SIPO. A simplified block diagram of digital
loopback is shown in Figure 17. Receive Data mute upon LOS, as shown in Figure 7, applies to Digital Local
FIGURE 17. DIGITAL LOCAL LOOPBACK
TX Parallel Input
Digital Loopback
PISO
Re-Timer
LVPECL
Output Drivers
TX Serial Output
RX Parallel Output
SIPO
CDR
LVPECL
Input Drivers
Loopback Mode
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