ARINC 429 defines the physical layer (shielded, twisted pair, differential, return to zero), the basic data unit (word), and a file transfer protocol. A 32-bit word encodes aircraft data as:

• BNR - binary, a two's complement representation of a real number
• BCD - binary coded decimal
• Discrete - boolean values coded into individual bits as 0 or 1

There are also wild combinations of those three and legacy encodings for generations of legacy equipment. This soapbox will discuss how to describe BNR encoding in a way that aligns with the ARINC 429 specification.