AN1278 datasheet(5/44 Pages) STMICROELECTRONICS

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LIN (LOCAL INTERCONNECT NETWORK) SOLUTIONS

The LIN protocol is object-oriented and not address-oriented. The header contains the identi-

fier which identifies the LIN frame and the data it contains. Different nodes may receive the

same frame data.

The response part consists mainly of data of selectable length (1 to 8 bytes). The data are se-

cured by an 8 bit checksum.

The LIN protocol is time-trigger oriented. The master periodically sends the same sequence of

LIN frames. Each sequence, the master and the slaves update the data they send and re-

ceive. The sequence sent by the master may change depending on application events.

Example: The slave is a sensor measuring a analog value which is communicated to the

master via LIN. The slave continuously measures its analog input independently from the LIN

communication. In response to a master request (periodical) the slave sends the up-to-date/

last measured value of the analog input.

Figure 3. Time-triggered protocol

In order to achieve a good level of security, different mechanisms exist like parity bits on the

identifier or checksum on data bytes.

One important feature of the protocol is to enable the slave MCUs to run with low cost oscilla-

tors such as an integrated RC oscillator provided that the accuracy is better than +/-15%. For

this purpose the header contains a sync field byte consisting of the constant 0x55. This byte

enables each slave to measure the master bit time and to synchronize its clock accordingly.

In order to obtain very low power consumption, the master is able to send a sleep frame. Any

node can go into low power mode. To wake up the network, any node can send a so-called

wake-up signal.

Master

Slave 1

Slave 2

1 sequence

Analog value:25

Analog

change

value

Analog value:38

LIN

Bus

AN1278 Datasheet(PDF) 5 Page - STMicroelectronics