Serial data

Overview

The term "Serial Data" refers to one of two methods by which most digital information is transmitted between devices. The devices can IC's on the same PC board, or separate units such as a personal computer and printer.

Basics

In order to represent a useful amount of information; most computer systems store and operate on information encoded in the form of a digital "word." A word is simply a specific number of "bits" that are grouped in a specific manner.

A bit is either a "1" or a "0" in binary math; which is the basis virtually all contemporary digital computation. Because one bit can only represent two "states" (one or zero); it is not useful for representing information that is not either "yes or no" or "on or off." By grouping bits in "columns;" a larger number of states can be represented.

For example: 8 bits can represent 256 states or "steps." 16 bits can represent 65,536 steps, and 24 bits can represent 16,777,216 steps. This is typically referred to as the resolution because in most applications it defines how "fine" the detail is of the coded information.

In early digital systems operating on 8 bit "words;" parallel transmission was commonly used both because the information contained in each "word" is only useful if it was present at the same time and because the frequency transmission of each word could be the same (or very close to the same)as of the clock used to synchronize the operation of all of the components in the system. This insured that each word would be passed from one device to the next once each clock cycle.

As the number of bits in the word increased; it is easy to see how the number of connections required would greatly increase to the point were parallel transmission of data became impractical.