Rockwell Automation 1747-SCNR ControlNet Scanner Module Reference Manual - Manual (Page 51)

Publication 1747-RM623D-EN-P - June 2006
Appendix A
Local Database Access Using
PLC-5 MSG Instructions
What This Appendix Contains This appendix describes how a PLC-5 processor reads or writes
data in the 1747-SCNR module Local Database using the
message (MSG) instruction.
What We Assume We assume that you know how to use the PLC-5 Message ladder
instruction.
Read and Write Access To
1747-SCNR Local Database
Using PLC-5 MSG Instruction The Local Database is used for direct read or write access from
the network. A remote PLC-5 processor can access this database
with MSG instruction as
described below.
The PLC-5 processor can read or write data in the 1747-SCNR
Local Database with the Message instruction. This instruction
creates unscheduled message connections that are initiated by
the PLC-5 processor and sent to the 1747-SCNR processor.
The 1747-SCNR scanner supports up to 50 simultaneous
unscheduled connections.
PLC-5 MSG instruction contains the following information:
• Command – Only PLC-5 Typed Read, PLC-5 Typed Write,
PLC-2 Unprotected Read, and PLC-2 Unprotected Write are
supported by the 1747-SCNR
• Data-table address in PLC-5 source processor
• Size of message in elements
• Network address of destination processor