SpaceWire Avionics Data Bus

	Enter your search terms Submit search form
	Web www.interfacebus.com

SpaceWire Description

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 (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

Engineering Design Key words: Avionic Buses, Bus Standard, Interface Standard Data Bus, Military Specification, MIL Spec, Interface, IC, Physical Interface, Description, Physical Interface, ARINC, MIL, Military, Defense, US, NATO, STANAG, ATR, Air, Aerospace, Aviation, Avionics, Aeronautical, Aircraft

Home
Distributors	Components	Equipment	Software	Standards	Buses	Design	Reference