Overview

Objective: The need for communication between system units, forming larger, integrated networks, and the need for large data-storage spaces are two fundamental components of modern digital designs. The digital codes employed in such cases are collectively known as line codes, while the corresponding data-protection codes are collectively known as error-detecting/correcting codes. With the integration of subsystems to perform these tasks onto the same chip (or circuit) that perform other, more conventional digital tasks, a basic knowledge of these techniques becomes indispensable to the digital designer. For that reason, an introduction to each one of these topics is included in this text with the former presented in this chapter and the latter in the next.

To a certain extent, line codes can be viewed as a continuation of Chapter 2, in which several binary codes were already described (for representing numbers and characters). Line codes are indispensable in data transmission and data storage applications because they modify the data stream, making it more appropriate for the given communication channel (like Ethernet cables) or storage media (like magnetic or optical memory). The following families of line codes are described in this chapter: Unipolar, Polar, Bipolar, Biphase/ Manchester, MLT, mB/nB, and PAM. In the examples, emphasis is given to Internet-based applications.

Chapter Contents