Does the FC block have a block interface

No, a Function (FC) block does not have a block interface like a Function Block (FB); it is stateless and only receives inputs and returns outputs during each call.Key Differences Between FC and FB

Function (FC) blocks in Siemens TIA Portal are stateless, meaning they do not retain internal memory between calls. They rely entirely on input parameters provided at the time of execution and return values through output parameters . Unlike FBs, FCs do not have an associated instance data block (DB) to store persistent data . This makes FCs suitable for simple, repeatable tasks where historical or ongoing state information is not required. Function Blocks (FBs), on the other hand, have a block interface through an instance DB, which stores input, output, in-out, and static variables. This allows FBs to retain state across scan cycles, making them ideal for controlling motors, timers, counters, or any process requiring memory of previous states . FBs can also implement interfaces, methods, and properties in object-oriented programming environments like TwinCAT .

Parameter Handling

• FCs: Parameters are passed by value for simple data types (INT, DINT, REAL) and by reference for complex types (ARRAY, STRUCT, STRING) to avoid unnecessary memory usage . FCs do not have a dedicated block interface; all data must be explicitly passed in and out during each call.
• FBs: Parameters are stored in the instance DB, allowing persistent storage and flexible access. FBs can be instantiated multiple times, each with its own memory, and can implement interfaces that automatically generate methods and properties .

Summary

• FCs: Stateless, no block interface, inputs/outputs only during call, suitable for simple logic.
• FBs: Stateful, have a block interface via instance DB, retain data across cycles, suitable for complex or memory-dependent logic. In conclusion, FCs do not have a block interface; they operate like standard functions in programming, while FBs provide a full block interface with persistent memory and object-oriented capabilities .