Spacewire Physical Layer Transceiver
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.
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 [www.ieee.org]
esa: European Space Agency [www.esa.int]
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.
5962-06232; Microcircuit, Digital, Radiation Hardened, Spacewire Physical Layer Transceiver,
Monolithic Silicon
UT200SpWPHY01; SpaceWire physical layer transceiver [Flat pack]
UT200SpWPHY01; SpaceWire physical layer transceiver,
extended industrial temperature range
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.
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 wire gauge [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.
Refer to the link for 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.
| Pin | Signal name | Description |
| 1 | DIN+ | Data In |
| 2 | SIN+ | Strobe In |
| 3 | Inner Shield | Ground |
| 4 | SOUT- | Strobe Out |
| 5 | DOUT- | Data Out |
| 6 | DIN- | Data In |
| 7 | SIN- | Strobe In |
| 8 | SOUT+ | Strobe Out |
| 9 | DOUT+ | Data Out |
Dsub Connector Dimensions [Shell size]
Dsub Connector Insert Arrangement [Pin spacing]
Note that IEEE1355 uses a different D connector than SpaceWire.
Although the connector is still D-shaped, it is not a 9-pin D connector.
The IEEE1355 connector may also not be qualified for usage in space.
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