In this section the operation of a SpaceWire link is considered in more detail. SpaceWire is based on two previous standards IEEE 1355-1995 and ANSI/TIA/EIA-644.
The SpaceWire standard covers the physical connectors and cables, electrical properties, and logical protocols that comprise SpaceWire data links and networks which are defined in the following normative protocol levels:
- Physical Level – SpaceWire connectors, cables, cable assemblies and printed circuit board tracks.
Signal Level – signal encoding, voltage levels, noise margins, and data signalling rates used in SpaceWire. - Character Level – data and control characters used to manage the flow of data across a SpaceWire link.
- Exchange Level – protocols for link initialisation, flow control, link error detection and link error recovery.
- Packet Level – definition of how data for transmission over a SpaceWire link is split up into packets
- Network Level – structure of a SpaceWire network and the way in which packets are transferred from a source node to a destination node across a network. The network level also defines how link errors and network level errors are handled.
In the following subsections each of these protocol levels will be considered in turn up to and including the exchange level.