Rockwell Automation 1763 MicroLogix 1100 Programmable Controllers User Manual - Manual (Page 205)

Publication 1763-UM001D-EN-P - March 2011
Connecting to Networks via RS-232/RS-485 Interface 203
Using Modems with MicroLogix™ Programmable Controllers
The types of modems you can use with MicroLogix™ controllers include the
following:
• dial-up phone modems.
A MicroLogix™ controller, on the receiving end of the dial-up
connection, can be configured for DF1 Full-Duplex protocol with or
without handshaking. The modem connected to the MicroLogix
controller should support auto-answer. The MicroLogix 1100 supports
ASCII out communications. Therefore, it can cause a modem to initiate
or disconnect a phone call.
• 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 in a point-to-point topology supporting Full-Duplex
communications between two modems or in a multi-drop topology
supporting Half-Duplex communications between three or more
modems.
• radio modems.
Radio modems may be implemented in a point-to-point topology
supporting either Half-Duplex or Full-Duplex communications, or in a
multi-drop topology supporting Half-Duplex communications between
three or more modems. MicroLogix 1100 also supports DF1 Radio
Modem protocol.
• 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). Line
drivers are available in Full-Duplex and Half-Duplex models.
Allen-Bradley’s AIC+ Advanced Interface Converter is a Half-Duplex
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 (8000 feet when bridged).
For point-to-point Full-Duplex modem connections that do not require any
modem handshaking signals to operate, use DF1 Full-Duplex protocol with
no handshaking. For point-to-point Full-Duplex modem connections that
require RTS/CTS handshaking, use DF1 Full-Duplex protocol with
handshaking.
For radio modem connections, use DF1 Radio Modem protocol, especially if
store and forward capability is required.