Avionics Navigation Systems, 2nd Edition

15 Avionics Interfaces

15.1 INTRODUCTION

Interfaces are an integral part of any avionics navigation system. There is no value in a navigation system that can determine the position of its host vehicle if that position cannot be made known to the host and other avionics elements through some type of a signal interface. However, interfaces between the aircraft navigation system and the rest of the vehicle extend beyond the signal interface, commonly a data bus, to include displays for the flight crew and the maintenance crew, the power system, packaging and mounting, and a suitable operating environment.

15.2 DATA BUSES

Data buses are the cornerstone of modern integrated avionics systems. They are the principal means by which information is exchanged among the navigation and other systems. Data buses are the paths by which the necessary inputs are received by a system or subsystem to perform its process(es) and the paths by which the outputs from the process(es) are sent to users.

Data buses fall into one of two broad categories: simplex (one way) with a single transmitter and multiple receivers, and duplex (two way) with multiple transmitters and receivers. Also, there are at least two possible transmission media, wire or optical cable. Other important features of data buses are bus control, bit rate, and word and message structure.

For military aircraft the principal data bus is the MIL-STD-1553, Digital Time Division Command/Response Multiplex Data Bus. This bus is used on many ...