Rockwell Automation DeviceLogix System User Manual - Manual (Page 71)

Publication RA-UM003B-EN-P - February 2010 71
Bind Function Blocks with I/O Chapter 3
Set Assume Data Available
The Assume Data Available feature should be used when feedback
paths are involved in your logic; this feature assists the Function Block
Editor in determining the function block process order. When
feedback paths are used, the Function Block Editor’s execution order
algorithm may be unable to determine which function block needs to
be resolved first. In this case, you must specify which function block
will be evaluated first by designating that the Function Block Editor
should assume that data is available at a specific input. Once selected,
a double-headed arrow appears at the end of the wire indicating that
it has precedence in the logic.
TIP
Following a verify operation, the software may indicate that it
could not resolve the execution order. In this case, you just use
the Assume Data Available feature to resolve the conflict.