Applies To:
  • CitectSCADA 5.xx

The MODNET Protocol driver does not correctly resolve blocked requests for data types of more than 1 word (ie LONG & REAL) where they fall on mixed boundaries (i.e. even and odd) even though they do not overlap. Tags of these data types that fall on the edge of the block are only half read (or written?). For example a REAL in this case will be received as 0.00 regardless of actual value in the I/O Device.

No errors are reported when this problem is occurring.


This problem can be avoided by setting the citect.ini parameter


So that Citect will only compile with REALs / LONGs on odd boundaries. This is the default value, hence the problem will only occur with this parameter set to 0.

CIT has confirmed this to be a problem in Citect for Windows version 5.xx. We are researching this problem and will post new information here as it becomes available.