CN8380 Datasheet, PDF (28/91 Pages) Conexant Systems, Inc – integrated quad line interface unit unit for both 1.544 Mbps (T1) and 2.048 Mbps (E1) applications

2.0 Circuit Description
2.3 Receiver
CN8380
Quad T1/E1 Line Interface
2.3 Receiver
Bipolar AMI pulses are input on the receiver input pins, RTIP[n] and RRING[n].
The receiver recovers clock and data from the AMI signal which has been
attenuated and distorted due to the line characteristics. The AMI pulses are
converted into bipolar or unipolar, NRZ data and output on RPOSO[n] and
RNEGO[n], along with the recovered clock on RCKO[n]. Figure 2-3 illustrates
the relationship between the AMI received signal, the recovered clock, and the
data outputs. This section discusses each receiver block from the line input to the
digital outputs.
Figure 2-3. Receiver Signals
Internal
Equalized
Received
Signal
RCKO
RPOSO
(Bipolar)
RNEGO
(Bipolar)
RDATO
(Unipolar)
BPV
(Unipolar)
Data Slicer Level
(50% of Peak)
BPV
1
1
1
0
1
1
0
1
1
2.3.1 Data Recovery
The receiver recovers data by normalizing the input signal with an automatic gain
control (AGC) circuit, removing distortion with an equalizer, and extracting the
data using a data slicer. The transfer function of the equalizer is adjusted based on
the average peak value of the input signal. The AGC maintains the equalizer’s
average peak output level to a constant value. The data slicer compares the
equalizer output to a threshold value equal to 50% of the average peak equalizer
output level and produces both positive and negative pulse detect signals. The
data slicer outputs are re-timed using the recovered clock and routed to the RZCS
decoder (or to the JAT).
2-6
Conexant
N8380DSA
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