Identifier

What is the identifier?

The identifier designates the type of bus message. This means that every message type gets a number between 0 and 2048 or 536870912 (depending on the data format, see below). The abbreviated form is ID0 to ID2048 or ID536870912.

 

Data format

There are two different formats for the identifier:

• Standard format
  In standard format the identifier contains exactly 11 bits in every message . This means that 2048 (2¹¹) different types of messages can be distinguised. The standard format is designated CAN 2.0 A.
• Extended format
  Extended format is also called an "extended frame format" and provides 29 bits for the identifier in a bus message. In this format over 500 million (2²⁹) types of messages are distinguished. This format is normally designated as CAN 2.0 B or CAN ext.

Broadcast

Using the principle of content-oriented addressing, a bus message is received from all the connected CAN stations. But only the stations for which the message is relevant will interpret it. If no identifier is given, the message is interpreted from all stations. Such a message is called a "broadcast".