I/O Functions A set of I/O functions was defined and accepted as a part of the SERCOS interface; but, because the SERCOS interface was originally developed as a drive interface, these were not originally included in the formal IEC61491 standard. A document describing these functions and parameters is available from the SERCOS member organizations. The SERCOS I/O Technical Working Group is preparing a specification for an extended device profile for I/O, based on the existing SERCOS communication protocol. Modular I/O devices with bus couplers as well as simple block I/Os will be included. In order to minimize the costs of the bus interface, especially for simple I/O, an FPGA-based low-cost communication controller will be developed. Even in smaller quantities, the price is expected to be under $5.  The SERCOS I/O specification will be available in late 2006. First prototypes of the low-cost FPGA I/O controller, as well as corresponding product implementations, will be available in 2006.