The MutexLock function locks the communication lock (for SSCP server, Modbus server, LCD, ...). It has no parameters and always returns false. It can be used to protect the variable changes in a structure at the moment the structure is processed in ST: the block closes between MutexLock and MutexUnlock. The number of MutexLock and MutexUnlock calls must be equal. Lock is active in one cycle only: after a cycle finishes, the lock opens.