Rainbow Electronics ATmega64M1 - Manual (Page 201)

201
8209A–AVR–08/09
ATmega16M1/32M1/64M1
21.3 LIN Protocol
21.3.1 Master and Slave
A LIN cluster consists of one master task and several slave tasks. A master node contains the
master task as well as a slave task. All other nodes contain a slave task only.
Figure 21-1. LIN cluster with one master node and “n” slave nodes
The master task decides when and which frame shall be transferred on the bus. The slave tasks
provide the data transported by each frame. Both the master task and the slave task are parts of
the Frame handler
21.3.2 Frames
A frame consists of a header (provided by the master task) and a response (provided by a slave
task).
The header consists of a BREAK and SYNC pattern followed by a PROTECTED IDENTIFIER.
The identifier uniquely defines the purpose of the frame. The slave task appointed for providing
the response associated with the identifier transmits it. The response consists of a DATA field
and a CHECKSUM field.
Figure 21-2. Master and slave tasks behavior in LIN frame
The slave tasks waiting for the data associated with the identifier receives the response and
uses the data transported after verifying the checksum.
Figure 21-3. Structure of a LIN frame
master task
slave task
master node
slave task
slave node
1
slave task
slave node
n
LIN bus
Master Task
Slave Task 1
Slave Task 2
HEADER
RESPONSE
HEADER
RESPONSE
BREAK
Field
SYNC
Field
CHECKSUM
Field
DATA-0
Field Field
IDENTIFIER
PROTECTED
DATA-n
Field
Break Delimiter Response Space Inter-Byte Space Inter-Frame Space
RESPONSE HEADER
FRAME SLOT
Each byte field is transmitted as a serial byte, LSB first.