MIL-1553- What does it mean?

MIL-1553 was originally issued by the Department of1533 defines data flow, error handling and terminal
Defense for military applications. It defines standardsoperations requirements. A uniform approach to
for functional, mechanical and electrical characteristicsmessage transmission, data and error handling bus
of the serial data bus commonly used in the avionicscomponents and the associated interfaces, assures
of military aircraft. It was developed when theinteroperability. Specifically, multiplex data bus systems
integration of computers systems into military aircraftmust function asynchronously in command/response
became imminent. Prior to employment of the data busmode, with transmission occurring in half-duplex.
for digital communications, transmissions were carriedInformation transmission control resides solely with the
through cables. Erwin Gangl one of the earliestbus controller. Messages are formed by specified
scientists to work on this project set up a method tocommand, data, and status words. The standard
facilitate digital communications among all avionicsprovides a high degree of interoperability. Standard
systems, such as radar navigation and data displaysinterchangeability makes maintenance manageable and
by employing the serial data bus, rather than miles ofallows for a fair amount of innovation in employing
cable.various 1533-compliant components.
First seen in the 70's on military fighter jets, it is hasHardware
both military and civil applications. The standard coversBeyond the two-conductor, twisted, shielded, jacketed
the data bus and all associated interface electronics.cable requirement, the standard defines impedance,
1533 governs bus and terminal operation, data flow,attenuation, termination and stub requirements. This
error handling, hardware and wiring. Although newsection also governs the noise emitted by operations
technology would seem to threaten its longevity,as well the tolerance of data transmissions for noise in
durability of 1533 can be attributed to its vastthe environment. Given the challenging environments in
international installed base. With so many installations,which avionics components operate, strict standards
manufacture of compliant systems is still goodmust be employed with the physical construction of
business. So what is the scope of MIL-1533 and whatthe data bus and associated electronics.
does it mean in avionics?Redundancy
TestingAll standards for testing operations and hardware
To be 1533 compliant, all components must to workapply in their entirety to all redundant systems. There
properly under all environmental conditions to which itare additional requirements to isolate the redundant
will be subjected. Consider its application for devicescomponents to avoid a failure of one eliminating the
used on spacecraft which will be subjected toother as a viable back-up and support a high degree
temperature and electrical field extremes. MIL-1533of fault tolerance. In general, the standard provides for
does not specify the environmental conditions foronly one data bus being active at a time. The
testing. These will be determined by the intended useredundancy standards in MIL-1533 are flexible enough
of the specific device employing the multiplex data bus.to accommodate a variety of applications while still
Operations and Messagingmaintaining integrity in redundancy.