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Multiple Protocol Scans

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Good Morning

I have a program, in which I need to receive using RS232 from 2 different units (One is a hand held scanner, and one is an Inkjet printer)

I have configured both protocols correctly and I see in info mode that the PLC is receiving them, but the strings they are receiving are not being sent to the correct place (I don’t see where they go)


In the main program I set this


My thought was that when I set MB0 the plc would get the code from the barcode scanner and when I set MB121 the “from printer” code would be received




As you can see that when I get the correct result I would then go to the assembly code scan

I also set the Barcode scanner protocol and reset the printer protocol


However when I run the program, it doesn’t “see the scans”, however when I am in info mode I see them

Thoughts please, what am I doing wrong

Link to vlp program

Thanks In advance




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  • MVP 2023

Your Protocol Config in the posted program (thanks for posting, BTW) grabs COM2 in three separate places.  I have never tried this, but I don't have a good feeling about it.  It probably hogs the port for scan blocks associated with the same name.  Since Protocol Config Send to printer is last, that's probably the only scan block that works.

There's no rule that you can't call a Protocol Config multiple times from ladder logic on an as needed basis.

I would start troubleshooting this by creating a program with only one Protocol Config at a time and seeing if the associated Scan block behaves.

Joe T.

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