Appendix B—
Serial Interface
This appendix deals with RS-232-C (and RS-422-A) serial interface
connectivity.
SERIAL INTERFACE BASICS
RS-232-C, commonly referred to as RS-232, is a serial interface
communication standard developed by the Electronics Industries
Association (EIA) which defines communication signals, pin assignments,
and voltage levels.
The standard divides equipment into two categories:
•
Data Terminal Equipment (DTE)
•
Data Communication Equipment (DCE)
The two types of equipment are distinguished by their signals and pin
assignments, as shown in the table on the following page:
•
DTE devices transmit on Pin 2
•
DCE devices transmit on Pin 3
Computers and serial printers are usually DTE devices. Modems and
communication controllers are usually DCE devices.
The RS-232-C standard specifies more signals than are used, or needed,
in most data communication applications. However, for reference, the
table on the following page lists all communication signals, their
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