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Setting up a Read_Var command to have a M340 PLC read data directly from a supported TCP/IP device.

Goals and Symptoms

M340 PLC & READ_Var

Causes and Fixes

Open your Unity Project and create a new Ethernet Network

Configure the Ethernet network according to your application. Don't forget to Validate your changes.

Next Link the Network to the correct Ethernet port in the configuration

Next go to Tools and Project Settings

In the Project Settings that the last 3 items in the Data types field are checked off.
This will allow us to directly enter Arrays into our project rather than having to first declare them as variables.

Next add a ADDM block to your program, link the OUT pin to the ADR pin of the Read_Var block, and enter the appropriate String (according to your Network configuration) to the IN pin
Note: The Syntax of the IN parameter of the ADDM block for Ethernet is explained in additional FAQs.

For this Example the Net Link id "Ethernet_1" and the IP address of the TCP/IP device is
Remember that this input is a String so you need ' before and after the text.

Next configure the remaining parameters of the Read_Var block where:

OBJ = String declaring the type of object to read (%MW or %M)
NUM = The starting register address in the slave TCP/IP device of the object type
NB = The # of registers to read
GEST = Array of length 4 where the Management Exchange table for the Read_Var is located
RECP = Array of length NB to where the read information is to be stored.
Note: The Array's are of type INT if declared as variables.

Finally build, download, and run the program


Legacy KB System (APS) Data: RESL187363 V2.0, Originally authored by MiMe on 08/02/2007, Last Edited by MiMe on 07/19/2008
Related ranges: Modicon M340
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