Bus Length and Loading Limits of MIL-STD-1553 Buses 872483
The determination of the maximum bus cable length, distance between bus couplers, number of couplers, and length of stubs that may be used in a MIL-STD-1553B bus system application is a fundamental problem in any bus design. MIL-STD-1553B does not specify maximum bus length or maximum stub length. Only a suggested maximum stub length is given. The MIL-STD-1553 Multiplex Applications Handbook (MIL-HDBK-1553) gives very little additional guidance in this area.
Waveform distortion due to reflections at the bus couplers is the primary factor which sets the bus length and loading limits of a MIL-STD-1553B bus. Waveform distortion is investigated experimentally, explained by application of transmission line theory, and accurately predicted by a computer simulation program.
The results of tests performed on a number of different bus configurations having bus lengths up to 300 feet and up to 32 bus terminals are given. The tests include the use of 8-stub couplers on the bus as well as the usual single stub couplers. Waveform photographs are given for the various bus configurations. The test results are analyzed and compared to waveforms generated by a computer simulation of the MIL-STD-1553B buses. Practical cable length and loading limits of MIL-STD-1553B buses are formulated, based upon the experimental and theoretical results of this investigation.