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Details of SpaceWire Interface

The SpaceWire interface is a Point-to-Point cable bus used to handle payload data on-board a spacecraft. The SpaceWire specification defines the Physical, Electrical and Protocol layers of the interface. SpaceWire operates from 2Mbps to 400Mbps over a full-duplex point-to-point serial link over a distance of 10m. The SpaceWire interface is defined by the following organizations:

IEEE 1355.2: SpaceWire, based on the HIC(Heterogeneous InterConnect) (IEEE-1355) bus, and Low Voltage Differential Signaling (EIA-644).
SpaceWire is also controlled by the European Space Agency, for the ECSS [European Cooperation for Space Standardization].

ECSS-E-50-12 Defines the Mechanical, Electrical, and Protocol. At data rate of 100Mbaud (min.) over a distance of 10 meters  .

SpaceWire Standard

IEEE 1355.2: SpaceWire protocol, derived from
SpaceWire Serial Point-to-Point Links ECSS-E-50-12; Draft Issue C
SpaceWire Links, Nodes, Routers and Networks ECSS-E-50-12; Draft Issue 2
IEEE {Institute of Electrical and Electronic Engineers, Inc.}
esa {European Space Agency}

SpaceWire Electrical Description

SpaceWire uses LVDS, +/- 247mV to +/- 454mV. SpaceWire uses 'Data-Strobe' (DS) Encoding, at a minimum data rate of 2Mbps (before timing out). Normal data rates after 'start-up' are 100Mbps and 200Mbps. Modules initially operate at 10Mbps after a reset.

SpaceWire Signaling Description

SpaceWire Data is sent in characters which are formed by a 'Parity bit', 'Data-Control Flag', and 8 data bits {LSB to MSB}. SpaceWire uses Odd Parity, the Data Control Bit is low to indicate data. Control words are sent with only 2 data bits. SpaceWire uses 'Data-Strobe' (DS) Encoding. The strobe changes when the data remains constant between bit intervals ~ the clock may be recovered by XORing the Data and Strobe lines (also used by IEEE-1355, and IEEE-1394).

Control characters are sent with three bits preceded with a Parity bit. Time code characters are longer.
Flow Control Token; FCT: P100
Normal End of Packet; EOP: P101
Error End of Packet; EEP: P110
Escape; ESC: P111
Null; P1110100, {ESC / FCT} also sent to avoid a link disconnect
After 850nS the link is considered disconnected if no bits are received.

SpaceWire Connector/Cable Description

The cable used with SpaceWire consists of 4 Shielded Twisted Pairs (STP), with a differential impedance of 100 ohms, surrounded by another shield. The cable terminates on a 9-pin D connector, pinout below. The individual wires are 28 AWG [7 x 36 AWG stranded wire]. The entire wire bundle is 40AWG. The conductors are silver coated. The cable end uses a Plug, while the equipment side uses a socket. Din/Sin is connected to Dout/Sout on the far end. 9-pin Dsub connector manufacturers. The micro-miniature D-type connector must be qualified for space use. Each differential signal pair is defined to have a skew of no more than 0.1nsec/m