SpaceWire is a fieldbus, the ESA has specified in ECSS standardization. The bus system transports data serial full duplex at a speed of up to 200 Mbps. SpaceWire is based on the IEEE - 1355-1995 standard, which has been adapted to the requirements in space with respect to its robustness, power consumption and EMC. Some ambiguities were eliminated in the description and improves the link - state machine.