Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 49)

Publication AG-UM008C-EN-P - February 2005
Configuring Enhanced PLC-5 Processors 2-11
Configuring a DF1
Half-Duplex
Message-based Mode
Master Station
Choose message-based communication mode if you want to use MSG
instructions in user programming to communicate with one station at
a time. If your application uses satellite transmission or public
switched telephone network transmission, consider choosing
message-based. Communication to a slave station can be initiated on
an as-needed basis.
Also choose message-based mode when a redundant PLC-5 system is
being used as a master station. Connect both PLC-5 processor serial
ports to the master station modem through an RS-232 modem splitter
and precondition all MSG instructions with the Primary Processor
status bit.
With message-based mode, you do not have an active station file that
you can use to monitor station status. Also, you cannot implement
slave-to-slave messaging or slave programming over the telemetry
network.
To configure the processor for a master station using message-based
communication, place the processor in program mode and follow the
steps below using RSLogix 5:
1. Double-click on the Channel
Configuration file to bring up
the Edit Channel Properties
interface.
2. On the Channel 0 tab, choose
System (Master) for your
Communication Mode.
3. Configure the Serial Port,
Options, and Polling
parameters according to
Table 2.3.