17.3.3
Data Transport
Two types of data may be transported in a frame; signals or diagnostic messages.
• Signals
Signals are scalar values or byte arrays that are packed into the data field of a frame. A signal
is always present at the same position in the data field for all frames with the same identifier.
• Diagnostic messages
Diagnostic messages are transported in frames with two reserved identifiers. The
interpretation of the data field depends on the data field itself as well as the state of the
communicating nodes.
17.3.4
17.3.5
Schedule Table
The master task (in the master node) transmits frame headers based on a schedule table. The
schedule table specifies the identifiers for each header and the interval between the start of a
frame and the start of the following frame. The master application may use different schedule
tables and select among them.
Compatibility with LIN 1.3
LIN 2.1 is a super-set of LIN 1.3.
A LIN 2.1 master node can handle clusters consisting of both LIN 1.3 slaves and/or LIN 2.1
slaves. The master will then avoid requesting the new LIN 2.1 features from a LIN 1.3 slave:
• Enhanced checksum,
• Re-configuration and diagnostics,
• Automatic baud rate detection,
• "Response error" status monitoring.
LIN 2.1 slave nodes can not operate with a LIN 1.3 master node (e.g. the LIN1.3 master does
not support the enhanced checksum).
The LIN 2.1 physical layer is backwards compatible with the LIN1.3 physical layer. But not the
other way around. The LIN 2.1 physical layer sets greater requirements, i.e. a master node
using the LIN 2.1 physical layer can operate in a LIN 1.3 cluster.
17.4 LIN / UART Controller
The LIN/UART controller is divided in three main functions:
• Tx LIN Header function,
• Rx LIN Header function,
• LIN Response function.
These functions mainly use two services:
• Rx service,
• Tx service.
Because these two services are basically UART services, the controller is also able to switch
into an UART function.
206
ATmega16/32/64/M1/C1
7647F–AVR–04/09
ATMEL [ ATMEL ]
