Figure 1 of 1553B: Sample Multiplex Data Bus Architecture
This standard establishes requirements for digital, command/response, time division multiplexing (Data Bus) techniques on aircraft. It encompasses the data bus line and its interface electronics illustrated on figure 1, and also defines the concept of operation and information flow on the multiplex data bus and the electrical and functional formats to be employed.
Additional sentences were added to 1553B to clarify designer selected options. The basic difference between 1553A and 1553B is that in 1553B the options are defined rather than being left for the user to define as required. It was found that when the standard did not define an item, there was no coordination in its use. Hardware and software had to be redesigned for each new application. Therefore, the one primary goal of 1553B was to provide flexibility without creating new hardware and software designs for each new user. This was accomplished by specifying the “use of” rather than the requirement “to use” in the functional areas and by specifying the electrical interfaces explicitly so that compatibility between designs by different manufacturers could be electrically interchangeable.