Rockwell Automation Publication 2080-UM002M-EN-E - April 2022 61
Chapter 5 Communication Connections
Modbus RTU
Modbus is a half-duplex, master-slave communications protocol. The Modbus
network master reads and writes bits and registers. Modbus protocol allows a
single master to communicate with a maximum of 247 slave devices. Micro800
controllers support Modbus RTU Master and Modbus RTU Slave protocol. For
more information on configuring your Micro800 controller for Modbus
protocol, see the Connected Components Workbench Online Help. For more
information about the Modbus protocol, see Modbus Protocol Specifications
available from https://www.modbus.org
.
For information on Modbus mapping, see Modbus Mapping for Micro800
on
page 251.
To configure the serial port as Modbus RTU, see Configure Modbus RTU
on
page 68.
CIP Serial Client/Server – DF1
CIP Serial Client/Server allows CIP protocol to be used over a serial port. It is
typically used with modems. The advantage over non-CIP serial protocols is
that since the protocol is CIP, program downloads are supported including
CIP pass-through from the serial port to Ethernet.
ASCII
ASCII provides connection to other ASCII devices, such as bar code readers,
weigh scales, serial printers, and other intelligent devices. You can use ASCII
by configuring the embedded or any plug-in serial RS-232/RS-485 port for the
ASCII driver. See the Connected Components Workbench Online Help for
more information.
To configure the serial port for ASCII, see Configure ASCII
on page 70.
Modbus TCP Client/Server
The Modbus TCP Client/Server communication protocol uses the same
Modbus mapping features as Modbus RTU, but instead of the serial port, it is
supported over Ethernet. Modbus TCP Server takes on Modbus Slave features
on Ethernet.
No protocol configuration is required other than configuring the Modbus
mapping table. For information on Modbus mapping, see Modbus Mapping
for Micro800 on page 251.
Use MSG_MODBUS instruction to send Modbus messages over serial port.
Use MSG_MODBUS2 instruction to send Modbus TCP messages over
Ethernet port.
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