DS3172 datasheet(104/232 Pages) DALLAS

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10.10 Line Encoder/Decoder

10.10.1 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, the BPV detector will count pulses on the RLCVn pin.

See Figure 10-25 for the locations of the Line Encoder/ Decoder block in the DS317x devices.

Figure 10-25. Line Encoder/Decoder Block Diagram

DS3/E3

Transmit

LIU

IEEE P1149.1

JTAG Test

Access Port

Microprocessor

Interface

HDLC

FEAC

DS3 / E3

Transmit

Formatter

DS3 / E3

Receive

Framer

Trail

Trace

Buffer

DS3/E3

Receive

LIU

TAIS

TUA1

Clock Rate

Adapter

TX BERT

RX BERT

UA1

GEN

B3ZS/

HDB3

Encoder

B3ZS/

HDB3

Decoder

10.10.2 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.

10.10.3 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.

Zero suppression encoding converts an AMI bipolar data stream into a B3ZS or HDB3 encoded bipolar data

stream. A B3ZS encoded bipolar signal is generated by inserting a B3ZS signature into the bipolar data stream if

both the POS and NEG signals are zero for three consecutive clock periods. An HDB3 encoded bipolar signal is

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