EIA-422

From Wikipedia, the free encyclopedia

(Redirected from RS-422)

Jump to: navigation,
search

American national standard ANSI/TIA/EIA-422-B (formerly RS-422)
and its international equivalent ITU-T Recommendation V.11 (also
known as X.27), are technical standards that specify
the "electrical characteristics of the balanced voltage digital interface
circuit"[1].
It provides for data transmission, using balanced or
differential signaling, with unidirectional/non-reversible, terminated or
non-terminated transmission lines, point to point, or multi-drop. In contrast to
RS-485 (which is
multi-point instead of multi-drop) EIA-422/V.11 does not allow multiple drivers
but only multiple receivers.

The current title of the ANSI standard is TIA-422 Electrical
Characteristics of Balanced Voltage Differential Interface Circuits and is
now in revision B, published in May 1994, and was reaffirmed by the Telecommunications
Industry Association in 2005.

Several key advantages offered by this standard include the differential
receiver, a differential driver and data rates as high as 10 megabaud at 12 metres (40 ft). The
specification itself does not set an upper limit on data rate, but rather shows
how signal rate degrades with cable length. The figure plotting this stops at 10
Mbit/s.

EIA-422 only specifies the electrical signaling characteristics of a single
balanced signal. Protocols and pin assignments are defined in other
specifications. The mechanical connections for this interface are specified by
EIA-530 (DB-25 connector) or EIA-449 (DC-37 connector), however
devices exist which have 4 screw-posts to implement the transmit and receive
pair only. The maximum cable length is 1200 m. Maximum data rates are 10 Mbit/s
at 12 m or 100 kbit/s at 1200 m. EIA-422 cannot implement a truly multi-point
communications network (such as with EIA-485), however one driver can be
connected to up to ten receivers.

A common use of EIA-422 is for RS-232 extenders. In video
editing studios it is used to link control signals for all video and audio
players/recorders to a central control board. Also, an RS-232-compatible variant of
RS-422 using a mini-DIN-8 connector
was widely used on Macintosh hardware until
it was replaced by Intel's Universal Serial
Bus on the iMac
in 1998.

EIA-422 can interoperate with interfaces designed to MIL-STD-188-114B, but they
are not identical. EIA-422 uses a nominal 0 to 5 Volt signal while MIL-STD-188-114B
uses a signal symmetric about 0 V. However the tolerance for common mode voltage
in both specifications allows them to interoperate. Care must be taken with the
termination network.

EIA-423 is a
similar specification for unbalanced signaling.

When used in relation to communications wiring, RS-422 wiring refers to cable
made of 2 sets of twisted pair, often with
each pair being shielded, and a ground wire. While a double pair cable may be
practical for many RS-422 applications, the RS-422 specification only defines
one signal path and does not assign any function to it. Any complete cable
assembly (i.e. with connectors) should be labeled with the specification that
defined the signal function and mechanical layout of the connector, such as
RS-449.

Wikibooks has a book on the
topic of

Programming:Serial
Data Communications

This article was originally based on
material from the Free
On-line Dictionary of Computing, which is licensed under
the GFDL.

[edit]
External links

The Telecommunications Industry
Association

[edit]
References

^
TIA/EIA STANDARD, Electrical Characteristics of Balanced Voltage Digital
Interface Circuits, TIA/EIA-422-B, May 1994

[edit]
See also

B&B Electronics "RS-422 and RS-485 Application Note" B&B
Electronics Manufacturing Company, retrieved from [1]

National Semiconductor Application Note AN-1031 "TIA/EIA-422-B Overview",
January 2000, National Semiconductor Inc., retrieved from [2]

National Semiconductor Application Note AN-759 "Comparing EIA-485 and
EIA-422-A Line Drivers and Receivers in Multipoint Applications", February
1991, National Semiconductor Inc., retrieved from [3]

National Semiconductor Application Note AN-214 "Transmission Line Drivers
and Receivers or TIA/EIA Standards RS-422 and RS-423" August 1993, National
Semiconductor Inc., retrieved from [4]

Maxim IC Application Note 723 "Selecting and Using RS-232, RS-422, and
RS-485 Serial Data Standards" Dec 2000,

Maxim Integrated Products, Inc., retrieved from [5]

Texas Instruments Application Report "422 and 485 Standards Overview and
System Configurations" June 2002, Texas Instruments, retrieved from [6]

Texas Instruments Application Report "Comparing Bus Solutions" February
2004, Texas Instruments, retrieved from [7]

Retrieved from "http://en.wikipedia.org/wiki/EIA-422"

Categories: Serial
buses

Views

Article

Discussion

Edit
this page

History

Personal tools

Log
in / create account

Navigation

Main Page

Contents

Featured
content

Current
events

Random
article

Interaction

About Wikipedia

Community
portal

Recent
changes

Contact
Wikipedia

Donate to Wikipedia

Help

Search

Toolbox

What links
here

Related
changes

Upload file

Special
pages

Printable
version

Permanent
link

Cite
this page

Languages

Deutsch

Español

한국어

Italiano

Nederlands

日本語

Português

Русский

中文

This page was last modified 16:46, 15 November 2007.

All text is available under the terms of the GNU
Free Documentation License. (See Copyrights
for details.)
Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc., a
U.S. registered 501(c)(3)
tax-deductible
nonprofit charity.

Privacy
policy

About Wikipedia

Disclaimers