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How do I configure a READ_VAR in an M340 or M580 PLC to read a Floating Point (REAL) number?

Published date: 23 April 2018

The READ_VAR can only be configured using INT Arrays or Direct Address Arrays. In actuality, the READ_VAR brings in the contents of the remote memory location undisturbed. If at the remote device %MW100 was configured as a real number, this real number occupies %MW100 and %MW101. The READ_VAR will read this back as %MW100 INT and %MW101 INT. You should then create a variable of data type REAL and locate it to %MW100, it will display the same number as the remote device in REAL format. There are other ways to use the data once you have it in the local PLC, but this was just meant to clarify the process.
***Note: if your REAL data comes in on an ODD numbered %MW, you will need to move it to an EVEN numbered %MW as M340 REALs must start on an EVEN number.


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