Functions (FUN) are Program Organization Units (POUs) that upon execution deliver a data element as a result and any number of output values of the classes VAR_OUTPUT and VAR_IN_OUT. By specifying the result type VOID the function has no result.
They can also access global variables via VAR_EXTERNAL, VAR_EXTERNAL_RETAIN or VAR_EXTERNAL_CONSTANT.
Functions do not contain any internal status information, i.e. calling a function with the same input values for the classes VAR_INPUT, VAR_IN_OUT and VAR_EXTERNAL will always yield the same result and the same output values for the classes VAR_OUTPUT, VAR_IN_OUT and VAR_EXTERNAL.
Control FPWIN Pro7 provides two types of functions:
System instructions of the system libraries
IEC standard library
FP library
FP tool library
FP pulsed library
User-defined functions
You can also program your own functions and store them in a user library. The new functions will then be available in all projects in which the user library is installed.
Functions can be written in the following programming languages:
Ladder diagram (LD) or Function block diagram (FBD)
Structured text (ST)
Instruction list (IL)
Functions cannot be assigned to a task as they can only be loaded by a program, function or function block.
A function cannot be called recursively.
FUN1() -> FUN2() -> FUN3() -> FUN1() is not allowed.
FUN1 (FUN2 (FUN3 (FUN4 (FUN5 (x))))), may not be exceeded.
Maximum of nested function calls |
PLC types |
|---|---|
16 |
FP7 |
10 |
Newer 16-bit PLC types like FP0H, FP_XH, FP0R |
15 |
Older 16-bit PLC types |
Except for ST or IL functions without formal parameters, function results and function outputs can be left unconnected.
When calling a function with formal parameters in the ST editor, the following conditions apply:
For arguments with formal parameters, the order of parameters does not matter.
With user functions, the EN input and output can be omitted. Omitted EN will be interpreted as TRUE.