Nicolais, Ray; Ellis, Donald H.; AEROSYSTEMS ASSOCIATES; AYDIN VECTOR Division (International Foundation for Telemetering, 1982-09)
      With the advent of digital technology in aircraft systems, the need for advancements in digital data acquisition systems for flight testing became apparent. A thorough review of aircraft systems integration employing the MIL-STD-1553 multiplex data bus revealed the need for flight test systems that incorporate the advanced digital techniques and provide an interface to the data bus. This paper provides an overview of the MIL-STD-1553 requirements including word structure and protocol, with special emphasis on the requirements for synchronization and time tagging of the data acquired from the bus. The data bus is a serial digital transmission system for interchange of control signals, status and data between equipment internal to the aircraft (or other vehicle). The basic multiplexing technique is Time Division Multiplexing (TDM) with the information coded in 20-bit (16-bit data) words. The transmitted waveform is biphase operating at a bit rate of 1.0 megabit per second. Transmissions are bi-directional on a twisted pair shielded cable. The requirements for a bus monitor unit which interfaces with the data bus for acquisition and processing of information are described. The design for a Programmable Bus Monitor (PBM) is detailed. The PBM provides a highly flexible and effective interface between the MIL-STD-1553 data bus and an advanced digital flight test system.