Liu – line interface unit, General description, Features – Rainbow Electronics DS3170 User Manual
Page 112: Transmitter, Receiver, Detailed description, Liu – l, Nterface, Figure 9-30. liu functional diagram, 12 liu – line interface unit
DS3170 DS3/E3 Single-Chip Transceiver
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9.12 LIU – Line Interface Unit
9.12.1 General Description
The line interface units (LIUs) perform the functions necessary for interfacing at the physical layer to DS3 or E3
lines. The LIU has independent receive and transmit paths and a built-in jitter attenuator. See
for the
location within the DS3170 device of the LIU.
Figure 9-30. LIU Functional Diagram
DS3/E3
Transmit
LIU
IEEE P1149.1
JTAG Test
Access Port
Microprocessor
Interface
HDLC
FEAC
LLB
DL
B
DS3 / E3
Transmit
Formatter
DS3 / E3
Receive
Framer
Trail
Trace
Buffer
DS3/E3
Receive
LIU
TAIS
TUA1
Clock Rate
Adapter
TX BERT
RX BERT
PL
B
AL
B
UA1
GEN
B3ZS/
HDB3
Encoder
B3ZS/
HDB3
Decoder
9.12.2 Features
· Performs Receive Clock/Data Recovery and Transmit Waveshaping
· Jitter Attenuators can be Placed in Either the Receive or Transmit Paths
· Interfaces to 75W Coaxial Cable at Lengths Up to 380 meters (DS3), 440 meters (E3)
· Use 1:2 Transformers on Tx and RX
· Requires Minimal External Components
· Local and Remote Loopbacks
9.12.2.1 Transmitter
· Gapped clock capable up to 52MHz
· Wide 50 ±20% transmit clock duty cycle
· Clock inversion for glueless interfacing
· Unframed all-ones generator (E3 AIS)
· Line build-out (LBO) control
· Tri-state line driver outputs support protection switching applications
· Per-channel power-down control
· Output driver monitor
9.12.2.2 Receiver
· AGC/equalizer block handles from 0 to 15dB of cable loss
· Loss-of-lock (LOL) PLL status indication
· Interfaces directly to a DSX monitor signal (~20dB flat loss) using built-in preamp
· Digital and analog loss-of-signal (LOS) detectors (ANSI T1.231 and ITU G.775)
· Clock inversion for glueless interfacing
· Per-channel power-down control
9.12.3 Detailed Description
The receiver performs clock and data recovery from an alternate mark inversion (AMI) coded signal or a B3ZS- or
HDB3-coded AMI signal and monitors for loss of the incoming signal. The transmitter drives standard pulse-shape