Guide to Selecting and Using RS-232, RS-422, and RS-485 Serial Data Standards

Abstract: Three common serial data standards, RS-232, RS-422, and RS-485, are described by specification and electrical interface. Cable termination techniques, use of multiple loads, daisy-chaining of RS-232, conversion of RS-232 to RS-485, conversion of RS-485 to RS-232, and RS-232 port-powered RS-485 conversions are described.