Do not fill in the parameters when calling the FC block interface

You can call an FC block without explicitly filling its parameters, as the FC uses stack memory to handle input values internally during execution.How FC Blocks Handle ParametersWhen an FC block is called, all input parameters are pushed onto the stack and assigned to internal memory locations within the FC. The FC then performs its logic using these internal copies of the parameters. After execution, only the return value (if any) is passed back to the calling program, and all temporary memory used for the parameters is discarded . This means that filling parameters is not strictly required if the FC logic does not depend on external values or if default values are acceptable.Call-by-Value vs Call-by-ReferenceCall-by-value: The FC copies the actual parameter values into its internal memory. This is typical for simple data types like INT, DINT, or REAL .Call-by-reference: The FC references the memory address of the parameter, which is more common for complex data types like STRUCT, ARRAY, or STRING. This avoids unnecessary memory copying . For FC blocks, simple data types are usually passed by value, so leaving parameters empty will not affect the stack allocation, but the logic may produce default or zeroed results if no values are provided.Differences from FB BlocksUnlike FB blocks, which require an instance data block (DB) to store persistent parameter values and internal states, FC blocks do not maintain internal memory between calls. Each call to an FC is independent, and parameters are allocated on the stack for that call only . This is why FCs are often used for stateless operations or calculations where persistent memory is not needed.Practical ImplicationsYou can safely call an FC without filling parameters if the logic allows default or zero values.If the FC requires specific input values for correct operation, you must provide them; otherwise, the output may be incorrect.Using FCs without parameters is memory-efficient because no additional data copying occurs beyond the stack allocation . In summary, FC blocks are designed to handle parameters dynamically on the stack, so leaving parameters empty is possible, but the behavior depends on the FC's internal logic and whether it expects meaningful input values .