The MIL-STD-1553 – A Simple Explanation

In 1973, the United States Air Force published the MIL-STD-1553 defining its standard for the mechanical, electrical characteristics for use as a data bus in military avionics. It was implemented on F-16 Falcon fighter jet. The United States Department of Defense adopted the standard, and it has expanded to include civil aircraft and it’s in the space program because of its reliability. MIL-STD-1553 is still the military standard but has been revised several times over the years. It’s been adopted by NATO and other world governments.

MIL-STD-1553 defines the Digital Time Division-Command Response Data Bus. The data bus has dual redundancy, and it’s bi-directional. It has high bit error reliability controlled through the main bus controller. A single main bus controller initiates and controls all bus communications, and it allows for the response of and attachment of remove devices under controller commands. It is effective, and reliable with a one Mbps transfer rate. The error rate is a one-word fault per 10 million because of its dual redundant architecture, and it’s used across a wide range of military systems.

Data is transmitted in digital form by bit priority and transferred over the bus by pulse code. Word size is 16 bits, and data words are transferred at the rate of one Mbps offering short and long-term accuracy. Data words contain the information transmitted to a remote terminal or bus controller. Status words transmit conditional information. If the remote transmitter detects the existence of an error, an error bit is transmitted.

How It Works
The bus controller (BC) issues commands followed by the proper data words. After verification, the remote terminal (RT) transmits a status word back to the BC. The stream of communication is constant between the BC and RT. The RT also transmits to other RTs directed by the BC without gaps, and after the transmission is received without error, a status word is transmitted back to the BC through the first RT.

Other appropriate word transmissions are used within the applications, and error testing and fail-safe systems are built in. Redundancy is implemented according to individual applications. Traffic on the data bus is constantly monitored ensuring system integrity, and the MIL-STD-1553 allows for external terminal addressing.

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