In many communication and networking systems, the signal transmitted on the communication line uses a non- return-

Question:

In many communication and networking systems, the signal transmitted on the communication line uses a non- return- to- zero (NRZ) format. USB uses a speciic version referred to as non- return- to- zero inverted (NRZI). A circuit that converts any message sequence of 0s and 1s to a sequence in the NRZI format is to be designed. The mapping for such a circuit is as follows:

(a) If the message bit is a 0, then the NRZI format message contains an immediate change from 1 to 0 or from 0 to 1, depending on the current NRZI value.

(b) If the message bit is a 1, then the NRZI format message remains fixed at 0 or 1, depending on the current NRZI value.

This transformation is illustrated by the following example, which assumes that the initial value of the NRZI message is 1: