XRT91L32 View Datasheet(PDF) - Exar Corporation
Part Name
Description
MFG CO.
'XRT91L32' PDF : 37 Pages View PDF
XRT91L32
STS-12/STM-4 OR STS-3/STM-1 SONET/SDH TRANSCEIVER
xr
REV. 1.0.2
2.0 RECEIVE SECTION
The receive section of XRT91L32 include the inputs RXIP/N, followed by the clock and data recovery unit
(CDR) and receive serial-to-parallel converter. The receiver accepts the high speed Non-Return to Zero (NRZ)
serial data at 622.08 Mbps or 155.52 Mbps through the input interfaces RXIP/N. The clock and data recovery
unit recovers the high-speed receive clock from the incoming scrambled NRZ data stream. The recovered
serial data is converted into an 8-bit-wide, 77.76 Mbps or 19.44 Mbps parallel data and presented to the
RXDO[7:0] parallel interface. This parallel interface is designed for Single-Ended LVTTL operation. A divide-
by-8 version of the high-speed recovered clock RXPCLKOP/N, is used to synchronize the transfer of the 8-bit
RXDO[7:0] data with the receive portion of the framer/mapper device. Upon initialization or loss of signal or
loss of lock, the external reference clock signal of 19.44 MHz or 77.76 MHz is used to start-up the clock
recovery phase-locked loop for proper operation. In certain applications, the CDR block on the XRT91L32 can
be disabled and bypassed by enabling the CDRDIS pin to permit the flexibility of using an externally recovered
receive clock thru the XRXCLKIP/N pins.7
2.1 Receive Serial Input
The receive serial inputs are applied to RXIP/N. The receive serial inputs can be AC or DC coupled to an
optical module or an electrical interface. A simplified DC coupling block diagram is shown in Figure 3.(For AC-
FIGURE 3. RECEIVE SERIAL INPUT INTERFACE BLOCK
RXIP
RXIN
XRT91L32
STS-12/STM-4
or
STS-3/STM-1
Transceiver
Install terminators as close
to RXIP and RXIN pins
120
Optical Module
82
1k
Tie unused differential input pins
to VCC and GND
XRXCLKIP
1k
XRXCLKIN
(optional)
Optical Fiber
coupled applications, refer to application note TAN-9130.)
NOTE: Some optical modules integrate AC coupling capacitors within the module. AC or DC coupling is largely specific to
system design and optical module of choice.
12
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