Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 75)

Publication AG-UM008C-EN-P - February 2005
Configuring MicroLogix 1100/1200/1500 Controllers 3-7
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-multipoint
topology supporting half-duplex communications between three or
more modems. In the point-to-point topology, configure the
MicroLogix 1100/1200/1500 controllers for DF1 full-duplex protocol
with the control line parameter set to Full-Duplex Modem. In the
point-to-multipoint topology, configure the MicroLogix
1100/1200/1500 controllers for DF1 half-duplex master or slave
protocol with the control parameter set to Half-Duplex Modem
(RTS/CTS Handshaking).
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-multipoint topology supporting half-duplex communications
between three or more modems. In the point-to-point topology using
full-duplex radio modems, configure the MicroLogix 1100/1200/1500
for DF1 radio modem protocol. In the point-to-multipoint topology
using half-duplex radio modems, configure the MicroLogix
1100/1200/1500 for DF1 radio modem protocol. If these radio
modems require RTS/CTS handshaking, configure the control line
parameter to Half-Duplex Modem (RTS/CTS Handshaking).
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).
Allen-Bradley’s 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 MicroLogix
1100/1200/1500 controllers for DF1 radio modem protocol. In a
point-to-multipoint line driver topology, configure the MicroLogix
1100/1200/1500 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 (RTS/CTS Handshaking).