TM

USING THE UNIVERSAL DATA

TRANSCEIVER FOR PROTOCOL

CONVERSION

MARKET: Data Transmission

DOC. NUMBER: T-06

setting each transceiver for the desired input and

output protocol. The circuitry does the rest. The ac-

In a fiber optic data transmission system, it is

companying diagram shows just how simple a typi-

sometimes necessary to convert from one protocol

cal RS-232 to RS-422 conversion can be.

into another so that different types of equipment may

“talk” to each other. When converting from RS-232

The Universal Data Transceiver can also

into RS-422 or RS-485, for example, external “pro- accomodate RS-485 two-wire conversions to and

tocol” converters are often used to make the proper from RS-232 or RS-422. When performing such con-

conversion. These must be mounted in the vicinity versions, the transceiver units use the same two sig-

of the fiber optic transmitters and receivers, adding nal leads for both transmitting and receiving data.

to the cost and complexity of the installation.

Therefore, it is necessary for the units to alternately

switch between a transmit and receive state. The

This TECHnique describes how the FIBERLINK

units can either be “told” when this switch must oc-

model 5012 Universal Data Transceiver can pro-

cur by an externally provided signal, often referred

vide a desirable alternative to using protocol

to as the RTS or

return to sender

line, or by inter-

converters within a fiber optic transmission system.

nally sensing the actual data being transmitted. Dip

This easy-to-use unit performs such conversions di-

switches allow the user to select whether the exter-

rectly, without the need for any additional equipment,

nal or internal method will be used. When the exter-

thereby resulting in a much simpler installation.

nal mode is selected, the system software provides

the enable signal and the unit switches whenever

the enable (RTS) line goes high. When the internal

data sense mode is used, the leading edge of data

The Universal Data Transceiver, designed to sup- being received enables the output driver. After the

port RS-232, RS-422 and RS-485 signals, converts transmission of the last data character, the trans-

all data passing through it into pulses of light. All ceiver then waits one character time before revert-

protocols are reduced to this common denominator ing to the receive mode. Provision is made to adjust

by the unit’s internal circuitry. Because of this, con- this “waiting” or “turn-around” time interval for the

verting from one protocol to another is as simple as most commonly used data rates.

Fiberlink is a trademark of Communications Specialties, Inc.

© 1999, Communications Specialties, Inc.



Page 2:

USING THE UNIVERSAL DATA TRANSCEIVER FOR

PROTOCOL CONVERSION

When using more than one protocol, be certain

that the various signal types, data rates and waiting

states can by accommodated by the software in use

by the overall system. This is particularly important

when using slow RS-232 equipment in conjunction

with much faster RS-422 equipment. When com-

bining RS-485 and RS-232 or RS-422 equipment,

be sure that the software in use allows for turn-

around times, as well as for the number of times a

master will “poll” a local unit before an error is de-

tected.

Also, remember to pay attention to the polarity of

the various protocols. Simply interchanging the

+ and – data leads can mean the difference between

proper operation and no operation at all.

•

Educational Guide:

An Introduction to

Fiber Optics

•

Educational Guide:

An Introduction to Fiber

Optic Cable and Connectors

•

Universal Data Transceiver ....................... 5012

Fiberlink is a trademark of Communications Specialties, Inc.

© 1999, Communications Specialties, Inc.