The Serial Standard Interface and Communication System

Abstract

Entirely different standard systems, primarily intended for data transfer rather than instrumental control, are used for connecting computers to the telephone system and one of these has become popular for the connection of peripherals, such as microcomputers or printers, to laboratory instruments. This is the RS232 standard of the Electronic Industry Association, which has undergone two revisions and in its present form is called the RS232C standard. This often provides a convenient means of connecting a microcomputer to a commercial instrument equipped with an RS232C interface, particularly as many computers (such as the Amiga, Atari, Macintosh and many PCs) are now fitted with RS232C-compatible ports, or have RS232C interfaces available as extras. In fact it is intended that the RS232C standard will gradually be replaced by the RS449 and RS422 standards which make allowance for the electrical characteristics of modern integrated circuits and permit greater operating distances and data transfer speeds. However, it is also intended that equipment conforming to the newer standards can interoperate with equipment designed to RS232C standard, and yet another standard, the RS423, exists to provide a high degree of compatibility with RS232 systems while conforming to the electrical and mechanical specifications of the RS449 and RS422 standards. As the overwhelming majority of the serial interfaces on microcomputer and laboratory equipment currently available are claimed to be RS232C standard, this discussion will be concentrated on that standard.