The CTAPI has been designed to be called from external applications. This API has not been designed to be called from the CitectSCADA Cicode DLL functions or from a CitectSCADA protocol driver. Calling the CTAPI from Cicode DLL functions or a CitectSCADA protocol driver may cause a deadlock condition to occur. This will result in CitectSCADA and the protocol driver hanging. If you need to call the CTAPI from a protocol driver, you need to create a new Win32 thread to call the API. You cannot call the CTAPI from the Cicode DLL interface.