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The received 4 data bits previous to reception of the violation

pulse have not been the sequence BX00 (where X = don't

care). The error signal (ERR) remains low.

NOTES:

1. The data sequences B000V and BB00V are valid HDB3 codings

of the NRZ binary sequence 10000.

2. The error signal (ERR) count, is the accurate number of all single

bit errors.

• AMl Signals HDB3/AMl = Low

- A coding error (ERR) is signaled when a violation pulse

(+V) is received.

• In Either the HDB3 or AMI Mode

- When high levels appear simultaneously on both HDB3

inputs (+ HDB3 IN, -HDB3 IN) a logical one is assumed

in the HDB3/AMl input stream and the error signal

(ERR) goes high for the duration of the violation.

Alarm Inhibit Signal

- The alarm output (AIS) is set high if, in two successive

periods of the external Reset Alarm Signal (RAlS), less

than three zeros are received.

- The alarm output (AlS) is reset low when three or more

zeros are received during two Reset Alarm Signal periods.

Transcoder Operation

Transmitter Coder (See Figure 1)

The HDB3/AMI transmitter coder operates on 4-bit serial

strings of NRZ binary data and a synchronous transmitter

clock (CTX). NRZ binary data is serially clocked into the

transmitter on the negative transition of the (CTX) clock.

HDB3/AMI coding is performed on the 4-bit string, and

HDB3/AMI binary output data is clocked out to the (+HDB3

OUT, -HDB3 OUT) outputs on the positive transition of the

transmitter clock (CTX) 3 1/2 clock pulses after the data

appeared at the (NRZ-IN) input.

Receiver Decoder (See Figure 2)

The HDB3/AMI receiver decoder operates on 4-bit serial

strings of binary coded HDB3/AMI signals, and a synchro-

nous receiver clock (CRX), HDB3/AMI binary data is serially

clocked into the receiver on the positive transition of the

(CRX) clock. HDB3/AMI decoding is performed on the 4-bit

string, and NRZ binary output data is clocked out to the

(NRZ-OUT) output on the positive transition of the receiver

clock (CRX) 4 clock pulses after the data appeared at the

(+HDB3 IN, -HDB3 IN) inputs.

HANDLING DELAY

NRZ - IN

+HDB3 OUT

HDB3

CODED

-HDB3 OUT

EXTERNAL GENERATED

TERNERY HDB3

+HDB3 OUT

AMI

CODED

-HDB3 OUT

EXTERNAL GENERATED

AMI

CTX

FIGURE 1. TRANSMITTER CODER OPERATION TIMING WAVEFORMS - NRZ TO HDB3/AMI CODING

CD22103A