42 Rockwell Automation Publication 5069-UM003B-EN-P - January 2020
Chapter 3 Compact 5000 I/O Serial Module Features
Leased-Line Modems
Leased-line modems are used with dedicated phone lines that are typically leased
from the local phone company. The dedicated lines may be point-to-point
topology supporting full-duplex communications between two modems or in a
point-to-multi-point topology supporting half-duplex communications between
three or more modems. In the point-to-point topology, configure the serial
module for DF1 full-duplex protocol with the control line parameter set to “Full-
Duplex Modem.” In the point-to-multi-point topology, configure the serial
module for DF1 half-duplex master or slave protocol with the control parameter
set to “Half-Duplex Modem without Continuous Carrier.” See DF1 Half-Duplex
Slave on page 43 for details on the operation of the RS-232 modem control
signals when “Half-Duplex Modem without Continuous Carrier” is selected.
Radio Modems
Radio modems may be implemented in a point-to-point topology supporting
either half-duplex or full-duplex communications, or in a point-to-multi-point
topology supporting half-duplex communications between three or more
modems. In the point-to-point topology using full-duplex radio modems,
configure the serial module for DF1 full-duplex protocol. In the point-to-multi-
point topology using half-duplex radio modems, configure the serial module for
DF1 half-duplex master or slave protocol. If these radio modems require RTS/
CTS handshaking, configure the control line parameter to “Half-Duplex Modem
without Continuous Carrier.”
Line Drivers
Line drivers, also called short-haul modems, do not actually modulate the serial
data, but rather condition the electrical signals to operate reliably over long
transmission distances (up to several miles). The Allen-Bradley AIC+ Advanced
Interface Converter is a line driver that converts an RS-232 electrical signal into
an RS-485 electrical signal, increasing the signal transmission distance from 50 to
4000 feet. In a point-to-point line driver topology, configure the serial module
for DF1 full-duplex protocol. In a point-to-multipoint line driver topology,
configure the serial module for DF1 half-duplex master or slave protocol. If these
line drivers require RTS/CTS handshaking, configure the control line parameter
to “Half-Duplex Modem without Continuous Carrier.”
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