Counting function
Using the editor in “select” mode, enter the instruction CTU (Count Up) into the ladder network:
Drop the IEC Function Block onto the empty Ladder network:
Instances of Function Blocks
Function Blocks can only be called as “Instances.” The process of “Instancing,” or making a
copy of a function block, is performed in the header of the POU in which the instance is to be
used. In this header the function block will be declared as a variable and the resulting instance is
given a name. It is possible to declare multiple instances with different names from one and the
same function block within the same POU. The instances are then called in the body of the POU
and the ‘Actual’ parameters are passed to the ‘Formal’ parameters. Each instance can be used
more than once.
Entering IEC Function Block CTU
햲
To create a new name for this instance of the CTU Function Block in this POU, click on the
variable name
Instance
above the CTU function block. And press F2 to bring up the
Vari
-
able selection
dialogue. Fill in the resulting window as shown on the next page.
Building a Project Application Program
Training Manual GX IEC Developer 4 - 25
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