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Preliminary
XRT91L31
STS-12/STM-4 OR STS-3/STM-1 SONET/SDH TRANSCEIVER
DEC 2006
REV. 1.0.2
parallel clock signal from the framer/mapper to
synchronize the transmit section timing. The device
GENERAL DESCRIPTION
The XRT91L31 is a fully integrated SONET/SDH
transceiver for SONET/SDH 622.08 Mbps STS-12/
STM-4 or 155.52 Mbps STS-3/STM-1 applications.
The transceiver includes an on-chip Clock Multiplier
Unit (CMU), which uses a high frequency Phase-
Locked Loop (PLL) to generate the high-speed
transmit serial clock from a slower external clock
reference. It also provides Clock and Data Recovery
(CDR) function by synchronizing its on-chip Voltage
Controlled Oscillator (VCO) to the incoming serial
data stream. The internal CDR unit can be disabled
and bypassed in lieu of an externally recovered
received clock from the optical module. Either the
internally recovered clock or the externally recovered
clock can be used for loop timing applications. The
chip provides serial-to-parallel and parallel-to-serial
converters using an 8-bit wide LVTTL system
interface in both receive and transmit directions.
The transmit section includes an option to accept a
can internally monitor Loss of Signal (LOS) condition
and automatically mute received data upon LOS. An
on-chip SONET/SDH frame byte and boundary
detector and frame pulse generator offers the ability
recover SONET/SDH framing and to byte align the
receive serial data stream into the 8-bit parallel bus.
APPLICATIONS
• SONET/SDH-based Transmission Systems
• Add/Drop Multiplexers
• Cross Connect Equipment
• ATM and Multi-Service Switches, Routers and
Switch/Routers
• DSLAMS
• SONET/SDH Test Equipment
• DWDM Termination Equipment
FIGURE 1. BLOCK DIAGRAM OF XRT91L31
STS-12/STM-4 or STS-3/STM-1
TRANSCEIVER
PISO
(Parallel Input
Serial Output)
TXOP/N
TXDI[7:0]
Re-Timer
8
ENB
ENB
TXPCLK_IO
Div by
8
REFCLKP/N
TTLREFCLK
CMU
RLOOPS
ALOOP
DLOOP
CDRAUXREFCLK
RXDO[7:0]
SIPO
(Serial Input
Parallel Output)
CDR
RXIP/N
8
XRXCLKIP/N
Div by 8
RXPCLKO
Control Block
Clock Control
Loop Filters
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (510) 668-7000 • FAX (510) 668-7017 • www.exar.com