TABLE OF CONTENTS D.A. Burt and K.D. Baker
Department of Electrical Engineering
Utah State University, Logan, Utah
The advent of digital electronics and instruments, computer-controlled instruments, and computer networks has spawned many different types of digital interface protocols to allow the transfer of data back and forth. Each standard was developed for a specific purpose, such as speed, reliability, cost, politics, copyrights, etc. An exhaustive description of all these standards is beyond the scope of this chapter; however, they all have similarities that we will try to describe. The practical considerations associated with the interchange of digital data between measuring instruments and between these instruments and the rest of the world will be briefly presented. These explanations will include voltage levels, limited bandwidth, jitter, noise effects, sensitivity, pulse rise time, data rate, and other errors.
When this type of transmission is used to transfer data in the form of a serial bit stream, the receiving system has no way of knowing when a transmission is going to occur or even when a data word is going to be transmitted. Usually, the bit rate is known, but each word has to carry a code that tells the receiver where the word begins and ends. This type of transmission is used for many applications. It is required where only one path is available, and the data must be sent in a serial manner. Examples of this are FAX machines, modems, teletypes, and serial computer peripherals. Theoretically, asynchronous transfer could be...
