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Configuration techniques
Input
parameters
Function
Action depending on
Input parameter
Output parameter
Evaluation
(optional)
Function with input and output parameters
Special case: program-controlled behavior
In the case described above, the behavior of the functions does not change during
runtime. However, in the case of some operating units and some functions, you
can also pass the value of a tag as an input parameter. The behavior of the
function can thus be controlled by the program.
General principle
The following figure illustrates the principle of how a function works:
Tag
Function
Tag
Constant
How a function works
An input parameter is specified for the function. This can be either constant or read
from a tag. The tag may be local or it may have a connection to the PLC. If there
is a connection to the PLC, the value is set by the process. The result of the
function is written to a tag, which itself can either be local or have a connection to
the PLC.
ProTool User’s Guide
Release 12/99
5-41