DS3181/DS3182/DS3183/DS3184
190
10.14 Line Encoder/Decoder
10.14.1 General Description
The B3ZS/HDB3 Decoder converts a bipolar signal to a unipolar signal in the receive direction. B3ZS/HDB3
Encoder converts a unipolar signal to a bipolar signal in the transmit direction.
In the transmit direction, the Encoder converts the unipolar signal to a bipolar signal, optionally performing zero
suppression encoding (HDB3/B3ZS), optionally inserting errors, and outputs the bipolar signal.
In the receive direction, the Decoder receives a bipolar signal, monitors it for alarms and errors, optionally
performing zero suppression decoding (HDB3/B3ZS), and converts it to a unipolar signal.
If the port line interface is configured for a Unipolar mode and the framer is not configured for one of the “-OHM”
modes, the BPV detector will count pulses on the RLCVn pin.
Figure 10-51 shows the locations of the Line
Encoder/Decoder block in the DS318x devices.
Figure 10-51. Line Encoder/Decoder Block Diagram
DS3/E3
Transmit
LIU
IEEE P1149.1
JTAG Test
Access Port
Microprocessor
Interface
HDLC
FEAC
LL
B
DL
B
DS3 / E3
Transmit
Formatter
DS3 / E3
Receive
Framer
Trail
Trace
Buffer
Tx Cell
Processor
Tx
FIFO
S
yst
em
In
te
rf
ac
e
Rx Cell
Processor
Rx
FIFO
Tx Packet
Processor
SL
B
Rx Packet
Processor
DS3/E3
Receive
LIU
TAIS
TUA1
TX FRAC/
PLCP
RX FRAC/
PLCP
Clock Rate
Adapter
TX BERT
RX BERT
PL
B
AL
B
UA1
GEN
B3ZS/
HDB3
Encoder
B3ZS/
HDB3
Decoder
10.14.2 Features
Performs bipolar to unipolar encoding and decoding – Converts a unipolar signal into an AMI bipolar signal
(POS data, and NEG data) and vice versa.
Programmable zero suppression – B3ZS or HDB3 zero suppression encoding and decoding can be
performed, or the bipolar data stream can be left as an AMI encoded data stream.
Programmable receive zero suppression code format – The signature of B3ZS or HDB3 is selectable.
Generates and detects alarms and errors – In the receive direction, detects LOS alarm condition BPV
errors, and EXZ errors. In the transmit direction, errors can be inserted into the outgoing data stream.
10.14.3 B3ZS/HDB3 Encoder
B3ZS/HDB3 Encoder performs unipolar to bipolar conversion and zero suppression encoding.
Unipolar to bipolar conversion converts the unipolar data stream into an AMI bipolar data stream (POS and NEG).
In an AMI bipolar data stream a zero is represented by a zero on both the POS and NEG signals, and a one is
represented by a one on a bipolar signal (POS or NEG), and a zero on the other bipolar signal (NEG or POS).
Successive ones are represented by ones that are alternately output on the POS and NEG signals. I.e., if a one is
represented by a one on POS and a zero on NEG, the next one will be represented by a one on NEG and a zero
on POS.