Rockwell Automation Publication 1766-UM001O-EN-P - September 2021 175
Appendix E
Connect to Networks via RS-232/RS-485
Interface
The following protocols are supported from the RS-232/RS-485 combination
communication channel (Channel 0) and the RS-232 communication channel
(Channel 2):
• DF1 Full Duplex
• DF1 Half-Duplex Master/Slave
• DF1 Radio Modem
•DH-485
• Modbus RTU Master/Slave
•ASCII
•DNP3 Slave
RS-232 Communication
Interface
The communications port on Channel 0 of the MicroLogix 1400 controller
utilizes a combined, isolated RS-232/RS-485 interface. RS-232 and RS-485 are
Electronics Industries Association (EIA) standards that specify the electrical
and mechanical characteristics for serial binary communication. They provide
a variety of system configuration possibilities (RS-232 and RS-485 define
electrical connection characteristics, not protocols).
The MicroLogix 1400 controller supports an additional, non-isolated RS-232
interface on Channel 2. One of the biggest benefits of an RS-232 interface is
that it lets you integrate telephone and radio modems into your control system
(using the appropriate DF1 protocol only, not DH-485 protocol), but it is for
point-to-point connections only between two devices.
RS-485 Communication
Interface
The RS-485 interface supports connection of devices in a multi-drop hard-
wired configuration using DH-485, DF1-Half Duplex, Modbus, or DNP3
protocols. Also, the RS-485 interface supports connection in a multi-drop hard-
wired configuration using ASCII protocols.
Topic Page
RS-232 Communication Interface 175
RS-485 Communication Interface 175
DF1 Full-Duplex Protocol 176
DF1 Half-Duplex Protocol 176
DH-485 Communication Protocol 179
Modbus Communication Protocol 185
ASCII 185
Distributed Network Protocol (DNP3) 185
Disable Serial Channels 0 and 2 185
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