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NOVEMBER 2001
XRT81L27
SEVEN CHANNEL E1 LINE INTERFACE UNIT WITH CLOCK RECOVERY
REV. 1.1.0
GENERAL DESCRIPTION
The XRT81L27 is an optimized seven-channel, ana-
log, 3.3V, line interface unit, fabricated using low pow-
er CMOS technology. The device contains seven in-
dependent E1 channels, including data and clock re-
covery circuits. It is primarily targeted towards the
SDH multiplexers that accommodate TU12 Tributary
Unit Frames. Line cards in these units multiplex 21 E1
channels into higher SDH rates. Devices with seven
E1 interfaces such as the XRT81L27 provide the
most efficient method of implementing 21-channel
line cards. Each channel performs the driver and re-
ceiver functions necessary to convert bipolar signals
to logical levels and vice versa.
The receiver input accepts transformer or capacitor
coupled signals, while the transmitter is coupled to
the line using a 1:2 step-up transformer. The same
transformer configuration can be used for both bal-
anced 120
Ω
and unbalanced 75
Ω
interfaces. The
Receiver Loss of Original Detection is compliant to
G.775 and in Host Mode, the number of zeros re-
ceived before RLOS is declared can be increased to
4096 bits. This feature provides the user with the flex-
ibility to implement RLOS specifications that require
greater than G.775 requirements
F
IGURE
1. B
LOCK
D
IAGRAM
SDO
SDI
SClk
CS
RST
LBM
LBEN
SR/DR
MODE
RClkP
ICT
MCLK
TClkP
TPOS_n
TCLK_n
TNEG_n
PDTx_n
TAOS_n
RClkP
Remote
Loopback
LOS
Detect
TCLKP
Encoded
PDATA
MCLK
FEATURES
•
Seven (7) Independent E1 (CEPT) Line Interface
Units (Transmitter, Receiver, and Recovery)
•
Transmit Output Pulses that are Compliant with the
ITU-T G.703 Pulse Template Requirement for
2.048Mbps (E1) Rates
•
On-Chip Pulse Shaping for both 75Ω and 120Ω line
drivers
•
Receiver Can Either Be Transformer or Capacitive-
Coupled to the Line
•
Detects and Clears LOS (Loss of Signal) Per ITU-T
G.775 and ETS 300 233 (programmable from Host)
•
Compliant with the ITU-T G.823 Jitter Tolerance
Requirements
•
3.3V operation with 5V Input compatibility
•
Low power consumption
APPLICATIONS
•
SDH and lPDH Multiplexers
•
E1 Digital Cross-Connect Systems
•
DECT (Digital European Cordless Telephone) Base
Stations
•
CSU/DSU Equipment
Microprocessor
Serial
Interface
(MSI)
Channel 6
Channel 5
Channel 4
Global
Control
Channel 3
Channel 2
Channel 1
Channel 0
Timing
Control
MUX
Timing
Control
TX
Pulse
Shaper
TTIP_n
Line
Driver
TRING_n
Encoder
Encoded
NDATA
Digital
Loopback
LOS_n
Analog
Loopback
RPOS_n
RClk_n
RNEG_n
Decoder
Data & Timing
Recovery
MUX
Peak
Detector
Receive
Equalizer
RTIP_n
RRING_n
Exar
Corporation 48720 Kato Road, Fremont CA, 94538
•
(510) 668-7000
•
FAX (510) 668-7017
•
www.exar.com
EXAR [ EXAR CORPORATION ]
