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View Full Version : ARINC 429 & 1553... what's the difference?


Captain Smithy
14th Dec 2009, 14:31
One for fellow avionics bods...

What's the difference between ARINC 429 & MIL-STD-1553? Can't work it out for myself because both seem to be the same thing...

Is 429 just the commercial (civvy) equivelant of 1553?

Ta

Smithy

Graybeard
14th Dec 2009, 15:39
A good example of both is in the Arinc 429 Wx radar.

The control bus - from the Control - sends mode, tilt, range, etc., to the transceiver on a 32-bit low speed Arinc 429 bus. 11KHz, IIRC.

The data bus out of the transceiver to the Displays, is a 1 MHz Arinc 1553 data bus. It repeats mode, tilt, range, etc., in the first 64 bits, then follows with 1500+ bits of azimuth/range bin data. The bits represent rainfall rate, doppler, etc. It's up to the display to determine the color to represent the contents of the azimuth/range bins.

I've never dicked with Mil 1553, but believe it is essentially the same as Arinc 1553.

GB

hugel
14th Dec 2009, 16:13
Both ARINC 429 and 1553B are communication standards for wiring and protocols widely used in civil and miltary aircraft applications.

During the early development of a spec suitable for aircraft use the civil designers judged a multiplexing databus to be too complex (cost, certification, compatibility with wide range of aircraft etc) and abandoned the 1553 development in favour of a simpler standard ARINC-419 and later ARINC-429.

The most significant difference (apart from speed and number of nodes possible) is that 1553 standard uses time-division multiplexing. This basically means multiple nodes - say sensors in the aircraft- can send their data "at the same time" along the same wire. (up to 31 at data speed up to 1M) It uses a command-response protocol.

ARINC 429 requires separate wires for transmit and receive at nodes (up to 20 data speed 100k), which means it's not a bus in the conventional sense as it requires more than one cable...

hugel

Captain Smithy
14th Dec 2009, 16:22
Thanks for the explanations.

Physically they seem to be the same (duplex twister-pair 78 Ohm wire) but I wasn't sure about the functionality of 429 vs. 1553. The system I currently am working with uses both protocols, as Greybeard alluded to.

Smithy

hugel
14th Dec 2009, 16:45
You're welcome. The 429 will normally have twisted pairs, one for transmit "source", one for receive "sink" (although it is usual not all nodes will require both, unless handshaking required). 1553 requires just the one twisted-pair, though you probably wouldn't notice is they were inside the same cable :ok:

hugel

hugel
14th Dec 2009, 16:51
Here is a couple of overview documents for 1553 (http://www.aim-online.com/pdf/OVW1553.PDF) and Arinc 429 (http://www.aim-online.com/pdf/OVIEW429.PDF) that you may find useful.

hugel

Graybeard
15th Dec 2009, 17:42
My mistake: the Arinc is 429 and 453, not 1553. All I wrote about 1553 is really 453.

The 78 ohm impedance is important only in 453, due to its high speed, not 429.

GB