CD22103A

The CD22103A is designed to code and decode HDB3 signals which are coded as binary digital signals (NRZ-lN) and (+HDB3 IN, -HDB3 IN), accompanied by sampling clocks (CTX) and (CRX). The two binary coded HDB3 outputs, (+HDB3 OUT, -HDB3 OUT) may be externally mixed to create the ternary HDB3 signals (See Figure 1).

The two binary HDB3 input signals have been split from the input ternary HDB3 in an external line receiver. CD22103A receiver decoder converts binary unipolar inputs (+HDB3 IN, -HDB3 IN), which were externally split from ternary bipolar HDB3 signals, and a synchronous clock signal (CRX) into binary unipolar NRZ signals (NRZ-OUT).

Received signals not consistent with HDB3 coding rules are detected as errors. CD22103A receiver error output (ERR) is active high during one CRX period of each bit of received data that is inconsistent with HDB3 coding rules.

CD22103A input string consisting of all ones (or marks) is detected and signaled by a high level at the Alarm Signal (AIS) output. The AIS output is set to a high level when less than three zeros are received during two consecutive periods of the Reset Alarm Inhibit Signal (RAIS). The AIS output is subsequently reset to a low level when three or more zeros are received during two periods of the reset signal (RAIS).

A diagnostic Loop-Test Mode may be entered by driving the Loop Test Enable Input (LTE) high. In CD22103A the HDB3 transmitter outputs (+HDB3 OUT, -HDB3 OUT) are internally connected to the HDB3 receiver inputs, and the external HDB3 receiver inputs, and the external HDB3 receiver inputs (+HDB3 IN, -HDB3 IN) are disabled. The NRZ binary output signal (NRZ - OUT) corresponds to the NRZ binary input signal (NRZ - IN) delayed by approximately 8 clock periods.

CD22103A Clock Receiver Output (CKR) is the product of the two HDB3 input signals or-ed together. The CRX clock signal may be derived from the CKR signal with external clock extraction circuitry. In the Loop Test Mode (LTE = 1) CKR is the product of the +HDB3 OUT and -HDB3 OUT signals or-ed together.

The CD22103A may also be used to perform the AMI to NRZ coding/decoding function. To use the CD22103A in this mode, the HDB3/AMI control input is driven low.