ICAO Doc 9871:2012

The purpose of this manual is to specify technical provisions for the formats and associated protocols used in Mode S services and extended squitter. The manual also includes implementation guidelines as well as information on future Mode S and extended squitter services that are under development. The provision of Mode S services, specified in this document, include the following: a) data formats for transponder registers; b) formats for Mode S specific protocols: traffic information broadcast; and dataflash; c) Mode S broadcast protocols, including: 1) uplink broadcast; and 2) downlink broadcast.