Is there a difference when using function block rather than functions in TwinCat?

Question

I started making the structure for a new PLC program, but I was wondering when is convenient to use a funtion rather than a function block, if there's any benefit on using them in TwinCat.

Answer 1

The defining characteristic is that a FUNCTION does not have internal memory of its variables.

• FUNCTIONs do not need to be instantiated before use
• FUNCTIONs re-instantiate their memory every time they are called

In contrast:

• FUNCTION_BLOCKs need to be instantiated before use ( to allocate their memory space )
• FUNCTION_BLOCKS will retain the status of their internal variables

This pretty much describes why you would use one over the other.

If you are writing a repeated segment of code that doesn't require memory of its previous state use a FUNCTION. Otherwise use a FUNCTION_BLOCK.