IFM Electronic CR0451 - Programming notes for CoDeSys projects

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ifm System Manual ecomatmobile BasicDisplay (CR0451) V01
Limitations and programming notes Programming notes for CoDeSys projects
6.2 Programming notes for CoDeSys projects
FB, FUN, PRG in CoDeSys .........................................................................................................40
Operating sequence.....................................................................................................................41
Creating application program .......................................................................................................42
CoDeSys visualisation elements (CR0451) .................................................................................43
Texts (CR0451) ............................................................................................................................44
Movement of elements.................................................................................................................44
Using ifm maintenance tool..........................................................................................................45
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Here you receive tips how to program the device.
► See the notes in the CoDeSys programming manual
 ecomatmobile DVD "Software, tools and documentation".
6.2.1 FB, FUN, PRG in CoDeSys
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In CoDeSys we differentiate between the following types of units (POUs):
FB = function block
 A FB may have several inputs and several outputs.
 A FB may be called several times within a project.
 For every call you must declare an instance.
 Allowed: in a FB call of FB or FUN.
FUN = function
 A function may have several inputs but only one output.
 The output is of the same data type as the function itself.
PRG = program
 A PRG may have several inputs and several outputs.
 A PRG may be called only once within a project.
 Allowed: in a PRG call of PRG, FB or FUN.
NOTE
Function blocks must NOT be called within a function.
Otherwise: During the executing the application program will crash.
POU-calls must not be recursive (POU must not call itself), also not indirectly.
Background:
By calling a function all variables...
- will become initialised and
- after return will lose their validity.
Function blocks have two calls:
- one initialising call and
- the call to do something.
Therefore, that means for a FB call inside a function, that there is every time an additional initialising
call.