Software Considerations for Interfacing Avionics Computers and Mux Buses

Desirable features for bus terminals that interface MIL-STD-1750 A avionics computers to MIL-STD-1553 B buses are discussed. Software considerations are emphasiszed: terminal features that simplify the attendant computer software for bus I/O, that minimize the burden on processor throughput, and that provide flexibility for handling variable bus traffic schedules.

The most challenging requirements arise in complex, multimode avionics systems with multiple computers interfacing via MUX buses. The computers are usually busy, and both the processing loads and bus interface loads vary among the several modes, so fixed, synchronous processing and bus schedules are not practical. It is often necessary to decouple the processors from one another, and execute the processing and the bus I/O asynchronously. Judicious design of a smart terminal can reduce the I/O interrupts and other burdens on the CPU, freeing it for its primary task of processing.