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Old March 15th, 2019, 02:12 PM   #1
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KingPresident is offline
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Location: Michigan
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MSG not pushing to buffer dint?

I have 2 configured PLC's that send and receive MSG's.


Set to CIP Data table Read
MSG Source is msgFROMplc2.dint[0]
MSG Dest is InputBuffer.dint[0]

I can send a value from PLC2, AND I can see it show up in PLC 1 at msgFROMplc2.dint[0], but the MSG will not push it to InputBuffer.dint[0]

However, I can use a MOV to move the value from msgFROMplc2.dint[0] to InputBuffer.dint[0] and it works, but I would think that it should be moved by the MSG instruction, not my additional MOV.

Clear as mud?
Is this normal, and if not, what am I doing wrong?

I am enabling and resetting every 1 second.
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Old March 15th, 2019, 02:48 PM   #2

gclshortt is offline
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The above thread may help you out.
You have not specified the PLC's that you are using.
"The MicroLogix 1400 doesn't know about CompactLogix tag names, so you have to take the extra step of setting up a "PLC/SLC Data Table Map" in the CompactLogix to correlate an INT or REAL[x] array tag to a Data Table address like N7 or F8."

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Old March 15th, 2019, 02:56 PM   #3
Ken Roach
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I can send a value from PLC2
Explain exactly what you mean by "send".

Some old platforms of PLCs required you to set up a Send instruction in one controller and a Receive instruction in another, as a matching pair. Allen-Bradley controllers do not.

A CIP Data Table Read instruction executed in "PLC-1" will request the value of the Source Element (msgFROMPLC2.dint[0]) from the other controller "PLC-2", and place its value in the Destination tag (InputBuffer.dint[0]).

You can choose to use CIP Data Table Read or CIP Data Table Write, as appropriate for your application.

But you only need one instruction for each transfer of data.
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Old March 18th, 2019, 11:30 AM   #4
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KingPresident is offline
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Location: Michigan
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Ken, thanks for that.

I was doing it wrong. I had MSG instructions on both plc's referencing the same tag.

Solution: I eliminated the MSG's on PLC2, now all works as intended. /thread.
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