What are the addresses for MODBUS / TCP of the variables in PAC Control?

I need to read and modify the variables from the PC via MODBUS / TCP, so I can program a strategy in the controller and at the same time access the variables from the PC, to graph them, modify the behavior of the controller by modifying the value of some variables and save the data on the hard drive of the PC. Is the address where the values of the variables are saved?

We have a SNAP-PAC-R2

The variables you create in PAC control are not directly available via Modbus, only items in the memory map are. In your strategy, you could transfer the variables to the “scratchpad” which is located in the memory map, and then they will be available through Modbus. If you already have a lot of invested Modbus code in your PC project or you HAVE to use Modbus, this may be the simplest way to get going.

Also, check out the REST API: http://developer.opto22.com/rest/pac/ You can get IO points and variables using it.

There is also a .NET Controller SDK that can read variables http://developer.opto22.com/dotnet/

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Thanks Philip, scratchpad is what I need, I’m going to study it and if I do not resolve to contact you.


The Modbus/TCP Protocol Guide may be helpful as well.



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