
Exar Corporation 48720 Kato Road, Fremont CA, 94538  (510) 668-7000  FAX (510) 668-7017  www.exar.com
XRT94L31
3-CHANNEL DS3/E3/STS-1 TO STS-3/STM-1 MAPPER IC
MARCH 2007
REV. 1.0.1
GENERAL DESCRIPTION
The XRT94L31 is a highly integrated SONET/SDH
terminator designed for E3/DS3/STS-1 mapping/de-
mapping functions from either the STS-3 or STM-1
data stream. The XRT94L31 interfaces directly to the
optical transceiver.
The XRT94L31 processes the section, line and path
overhead in the SONET/SDH data stream. The
processing of path overhead bytes within the STS-1s
or TUG-3s includes 64 bytes for storing the J1 bytes.
Path overhead bytes can be accessed through the
microprocessor interface or via serial interface.
The XRT94L31 uses the internal E3/DS3 De-
Synchronizer circuit with an internal pointer leak
algorithm for clock smoothing as well as to remove
the jitter due to mapping and pointer movements.
These De-Synchronizer circuits do not need any
external clock reference for its operation.
The SONET/SDH transmit blocks allow flexible
insertion of TOH and POH bytes through both
Hardware and Software. Individual POH bytes for the
transmitted SONET/SDH signal are mapped either
from the XRT94L31 memory map or from external
interface. A1, A2 framing pattern, C1 byte and H1, H2
pointer byte are generated.
The SONET/SDH receive blocks receive SONET
STS-3 signal or SDH STM-1 signal and perform the
necessary transport and path overhead processing.
The XRT94L31 provides a line side APS (Automatic
Protection Switching) interface by offering redundant
receive serial interface to be switched at the frame
boundary.
The XRT94L31 provides 3 mappers for performing
STS-1/VC-3 to STS-1/DS3/E3 mapping function, one
for each STS-1/DS3/E3 framers.
A PRBS test pattern generation and detection is
implemented to measure the bit-error performance.
A general-purpose microprocessor interface is
included for control, configuration and monitoring.
APPLICATIONS
 Network switches
 Add/Drop Multiplexer
 W-DCS Digital Cross Connect Systems
FEATURES
 Provides DS3/ E3 mapping/de-mapping for up to 3
tributaries through SONET STS-1 or SDH AU-3
and/or TUG-3/AU-4 containers
 Generates and terminates SONET/SDH section,
line and path layers
 Integrated SERDES with Clock Recovery Circuit
 Provides
SONET
frame
scrambling
and
descrambling
 Integrated Clock Synthesizer that generates 155
MHz and 77.76 MHz clock from an external 12.96/
19.44/77.76 MHz reference clock
 Integrated 3 E3/DS3/STS-1 De-Synchronizer circuit
that de-jitter gapped clock to meet 0.05UIpp jitter
requirements
 Access to Line or Section DCC
 Level 2 Performance Monitoring for E3 and DS3
 Supports mixing of STS-1E and DS3 or E3 and
DS3 tributaries
 E3 and DS3 framers for both Transmit and Receive
directions
 Complete Transport/Section Overhead Processing
and generation per Telcordia and ITU standards
 Single PHY and Multi-PHY operations supported
 Full line APS support for redundancy applications
 Loopback support for both SONET/SDH as well as
E3/DS3/STS-1
 Boundary scan capability with JTAG IEEE 11498-
bit microprocessor interface
 3.3 V ± 5% Power Supply; 5 V input signal
tolerance
 -40°C to +85°C Operating Temperature Range
 Available in a 504 Ball TBGA package