Editing Local Interconnect Network (section)

== LIN protocol ==
The LIN-Master uses one or more predefined [[I/O scheduling|scheduling]] tables to start the sending and receiving to the LIN bus. These scheduling tables contain at least the relative timing, where the message sending is initiated.
One LIN Frame consists of the two parts: '''header''' and '''response'''. The header is always sent by the LIN Master, while the response is sent by either one dedicated LIN-Slave or the LIN master itself.

Transmitted data within the LIN is transmitted serially as eight bit data bytes with one start bit, one stop-bit, and no parity (break field does not have a start or stop bit). Bit rates vary within the range of 1&nbsp;[[kbit/s]] to 20&nbsp;kbit/s.
Data on the bus is divided into recessive (logical HIGH) and dominant (logical LOW).
The time normally is considered by the LIN Masters stable clock source, the smallest entity is one [[bit time]] (52 μs @ 19.2&nbsp;kbit/s).

Two bus states{{dash}}sleep-mode and active{{dash}}are used within the LIN protocol. While data is on the bus, all LIN-nodes are asked to be in the active state. After a specified timeout, the nodes enter sleep mode and will be released back to active state by a WAKEUP frame.
This frame may be sent by any node requesting activity on the bus, either the LIN Master following its internal schedule, or one of the attached LIN Slaves being activated by its internal software application.
After all nodes are awakened, the Master continues to schedule the next Identifier.

===Header===
The header consists of five parts:

''BREAK:''
The BREAK field is used to activate all attached LIN slaves to listen to the following parts of the header. It consists of one start bit and several dominant bits. The length is at least 11-bit times; standard use as of today are 13-bit times, and therefore differs from the basic data format. 
This is used to ensure that listening LIN nodes with a main-clock differing from the set bus baud rate in specified ranges will detect the BREAK as the frame starting the communication and not as a standard data byte with all values zero ([[hexadecimal]] 0x00).

''SYNC:''
The SYNC is a standard data format byte with a value of hexadecimal 0x55. 
LIN slaves running on RC oscillator will use the distance between a fixed amount of rising and falling edges to measure the current bit time on the bus (the master's time normal) and to recalculate the internal baud rate.

''INTER BYTE SPACE:''
Inter Byte Space is used to adjust for bus jitter. It is an optional component within the LIN specification. If enabled, then all LIN nodes must be prepared to deal with it.

There is an Inter Byte Space between the BREAK and SYNC field, one between the SYNC and IDENTIFIER, one between the payload and Checksum and one between every Data byte in the payload.

''IDENTIFIER:''
The IDENTIFIER defines one action to be fulfilled by one or several of the attached LIN slave nodes. The network designer has to ensure the fault-free functionality in the design phase (one slave is allowed to send data to the bus in one frame time).

If the identifier causes one ''physical'' LIN slave to send the response, the identifier may be called a Rx-identifier.
If the ''master's slave task'' sends data to the bus, it may be called Tx-identifier.

''RESPONSE SPACE:''
Response Space is the time between the IDENTIFIER field and the first Data byte which starts the LIN RESPONSE part of the LIN frame. When a particular LIN frame is transmitted completely, Header + Response, by the LIN MASTER, the LIN MASTER will use the full RESPONSE SPACE TIME to calculate when to send the response after sending the header. If the response part of the LIN frame is coming from a physically different SLAVE NODE, then each node (master & slave) will utilize 50% of the Response Space time in their timeout calculations.

===Response===
The response is sent by one of the attached LIN slave '''tasks''' and is divided into data and [[checksum]].<ref name="SPEC" />

''DATA:''
The responding slave may send zero to eight data bytes to the bus. The amount of data is fixed by the application designer and mirrors data relevant for the application which the LIN slave runs in.

''CHECKSUM:''
There are two checksum-models available within LIN - The first is the checksum including the data bytes only (specification up to Version 1.3), the second one includes the identifier in addition (Version 2.0+).
The used checksum model is pre-defined by the application designer.