Rockwell Automation Publication 1766-UM001O-EN-P - September 2021 185
Appendix E Connect to Networks via RS-232/RS-485 Interface
Modbus Communication
Protocol
Modbus is a Half-Duplex, master-slave communications protocol. The Modbus
network master reads and writes coils and registers. Modbus protocol allows a
single master to communicate with a maximum of 247 slave devices.
MicroLogix 1400 controllers support Modbus RTU Master and Modbus RTU
Slave protocol.
For more information on configuring your MicroLogix 1400 controller for
Modbus protocol, see MicroLogix 1400 Programmable Controllers Instruction
Set Reference Manual, publication 1766-RM001
. For more information about
the Modbus protocol, see the Modbus Protocol Specifications (available from
http://www.modbus.org
).
ASCII ASCII provides
connection to ot
her ASCII devices, such as bar code readers,
weigh scales, serial printers, and other intelligent devices.
You can use ASC
II by configurin
g the RS-232/RS-485 port, channel 0 and the RS-
232 port, Channel 2 for the ASCII driver. For detailed configuration
information, see MicroLogix 1400 Programmable Controllers Instruction Set
Reference Manual, publication 1766-RM001
.
Distributed Network
Protocol (DNP3)
For more information on configuring your MicroLogix 1400 controller for
Distributed Network Protocol, see Channel Configuration for DNP3 Slave on
page 187. For more information about Distributed Network Protocol, see the
Distributed Network Protocol Specifications, available from http://
www.dnp.org.
Disable Serial Channels 0 and 2
In RSLogix 500 software, you can disable Serial Channels 0 and/or 2 to
enhance security.
1. Open the Channel Configuration in the MicroLogix 1400 project tree and
select a channel.
2. From the Driver drop-down list, select Shutdown.
3. Click Apply and OK.
The selected serial channels are disabled.
IMPORTANT At least 1 of the 3 channels must be active to enable communication with
the RSLogix 500 software. You cannot disable the last serial channel if the
other 2 channels (Serial, Ethernet) are already configured as disabled.
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