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Device Read Error with MicroLogix

Device Read Error on integer file read (example "N7:20")with Micrologix and SLC family of controllers is caused by polling an item that does not exist in the PLC by Interact/InteractX/Xress.

The underlying is caused is incorrectly dimensioning the integer file in the PLC. Polling N7:200 would generate the error if the integer file only has a size of 200 (N7:0 -> N7:199).

Once the CTC panel attempts to poll an item that is outside the integer file range ALL integer file requests will generate this error, even if they exist in the PLC.

The solution is to dimension a file larger than needed to ensure that adding items later would not cause errors.

edited DM 04/25/2016