Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 220)

Publication AG-UM008C-EN-P - February 2005
6-16 Configuring MicroLogix 1000 Controllers
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In a point-to-point configuration, the messaging would be
between the two connected peer devices.
The configuration of the network (point-to-multipoint vs.
point-to-point) and the configuration of the station (slave or peer)
does not affect how you configure an MSG instruction. That is, an
MSG instruction being sent between two MicroLogix slave stations is
configured the same as an MSG instruction between two MicroLogix
controllers connected point-to-point. See Figure 6.5 through
Figure 6.8 for example MSG control blocks.
Considerations When Configuring MSG Control Blocks
The MicroLogix 1000 can only execute 1 MSG instruction at a time.
Each MSG instruction should complete done or in error before the
next one is triggered.
Use the active protocol bit (S:0/11) as a pre-condition in the MSG
instruction rung to restrict message operation to a specific protocol.
This is a read-only bit that indicates which communication protocol is
currently enabled (0=DF1 and 1=DH-485).
Keep the following considerations in mind when configuring
messages between a MicroLogix 1000 controller and a PLC-5
processor:
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In the MicroLogix 1000 485CIF type MSG instruction, Target
Node is the decimal node address of the PLC-5 processor and
Targets CIF Offset is the decimal byte-offset, which is the
element you want to write data into or read data from.
Station 1
Station 2
MSG
Modem Modem