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LIN Protocol Overview:

Topology:

  • Broadcast serial network
  • 12v Bus with 16 nodes or less
    - based upon LIN specification and standard driver characteristics
    - LIN is limited to 64 identifiers and relatively low transmission speed.


LIN Protocol Overview:
  • Master Task
     - control over the whole Bus and Protocol: The master controls which message at what time is to be transferred over the bus.  It can also do the error handling.

- to accomplish this the master

  • sends Sync Break, Sync Byte & ID-Field
  • monitors Data Bytes and Check Byte, and evaluates them on consistence
  • receives Wakeup Break from slave nodes when the bus is inactive and they request some action
  • serves as a reference with it’s clock base (stable clock necessary)
  • Slave Task
     - one of 2-16 members on the bus and receives or transmits data when an appropriate ID is sent by the master.
  • Slave waits for Sync Break
  • Slave synchronizes on Sync Byte
  • Slave snoops for ID.
  • According to ID, slave determines what to do: either receive data, or transmit data or do nothing.

- When transmitting, the slave sends 2, 4, or 8 Data Bytes & Check-Byte.
- The node serving as a master can be slave.


LIN Protocol Overview:
  • Message Frame Header

- Sync Break:

Marks the Beginning of a Message Frame (less than 13 bit)

- Synch Field:

Specific Pattern for Determination of Time Base(Determination of the time
between two rising edges)

- ID-Field:

  • Message Identifier: Incorporates Information about the sender, thereceiver(s), the purpose, and the Data field length.
  • Length 6 Bit.
  • 3 classes of 2/4/8 Data Bytes. The length coding is in the
  • 2 MSB of the ID-Field. A total of 64 Message Identifiers ispossible.
  • 2 linked Parity Bits protect this highly sensitive ID-Field.
  • Message Frame Header

- Data Field:

  • 1-8 bytes in length, as determined during system configuration of the message frame ID’s.
  • may consist of one or more ‘signals’ appended together.

- Checksum Field:

  • consist of single byte.
  • defined as the 1’s complement sum of all data bytes.
  • LIN 1.3 and Diagnostic message frames: classic checksum.
  • LIN 2.0: Extended checksum-all data bytes plus the protected ID byte.


LIN Protocol Overview:

Physical Layer:

  • single-wire: ISO 9141 compliant
    - max 20% / min 80% VBAT Low/High transmit level
    - min 40% / max 60 % VBAT Low/High receive threshold
    - controlled slew rate (1-2 V/µs)

 



LIN Protocol Overview:

LIN Transfer Speed:

  • Speed up to 20K bit/sec:
    - Acceptable speed for many application (limited for EMI-reasons)
    - The recommended data rates are 2400bps, 9600bps and 19200 bps.
    - controlled slew rate (1-2 V/µs)
  • Data Format:
    UART/SCI base
    - Hardware or software (with standard I/O port)
    - Low cost silicon implementation based upon common UART/SCI interface
LIN Protocol Overview:

Guaranteed signal-transmission latency times:

  • Time Triggered Approach
- Message Length is known
  • Number of transmitted data bytes is known minimum length can be calculated
  • Each Message has length budget of 140% of it's minimum length
    - maximum allowed length is known
    - distance between beginning of two messages


- Message sequence is known

  • Master uses scheduling table

 


- Use of different scheduling tables is possible

 


Network configuration:

  • Standard LIN Description File
    - describes complete LIN network and also contains all information necessary to monitor the network.

 

 


  • Standard LIN Configuration Language
    - allows nodes to be used for various purposes without jeopardizing the LIN system functionality by message incompatibility or network overload.
    - is useful for debugging LIN clusters or diagnose the traffic. - provides “plug-and-play” capability with any off-the-shelf slave node MCUs.
  • Standard LIN API
    - simplifies Application code design.
    - enables to select any controllers that support LIN peripheral


Dynamic configuration:

  • Standard LIN Tool
    - LIN Database Manager (LDM):
    The LDM is a standalone offline tool, providing a user-friendly Windows interface for logically describing and configuring LIN systems at a high abstraction level.

    - LIN Configuration Tool (lcfg):
    The LIN API, together with the LIN Configuration Tool and an optimized embedded SW package enables the user to get correctness and quality together with efficiency and reconfiguration flexibility.

    - LINspector:
    a highly flexible tool for testing and verifying communication for compliance with the LIN standard.


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