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FAQ: LIN design

Posted: 15 Oct 2008 ?? ?Print Version ?Bookmark and Share

Keywords:FAQ? LIN? CAN?

What is LIN?
LIN (Local Interconnect Network) is a low cost serial communication system for distributed electronic systems in vehicles. It complements the existing portfolio of automotive multiplex networks. LIN enables cost-effective communication for smart sensors and actuators where the bandwidth and versatility of CAN is not required.

The Key Features of LIN are:

  1. Low cost single-wire implementation

  2. Enhanced ISO 9141, VBAT-Based

  3. Speed up to 20Kbit/s (limited for EMC reasons)

  4. Single Master/Multiple Slave Concept

  5. No arbitration required

  6. Low cost silicon implementation based on common UART/SCI interface hardware

  7. Self synchronization in the slave nodes without crystal or ceramics resonator

  8. Significant cost reduction of hardware platform

  9. Guaranteed latency times for signal transmission

  10. Predictable systems possible

Does LIN replace CAN?
No, LIN and CAN co exist in the automotive market.

LIN addresses an application space that requires less bandwidth and versatility when compared to the CAN application space.

What are the target applications for LIN Bus?
Target automotive applications include mirrors, window lift, doors switches, door lock, HVAC motors, control panel, engine sensors, engine cooling fan, seat positioning motors, seat switches, wiper control, light switches, interface switches to radio/navigation/phone, rain sensor, light control, sun roof, RF receivers, body computer/smart junction box, interior lighting and more.

Can LIN be used for non-automotive applications?
Although designed for automotive applications, LIN is not limited to automotive applications and has found it's way already into applications such as appliance and consumer.

What is the latest LIN Bus Specification?
In November 2006 LIN 2.1 has been released. No further changes are planned at this moment. Please check LIN home page (www.lin-subbus.de) for the latest status.

What is the compatibility between LIN 2.0 and 2.1?
A LIN 2.1 master node may handle a LIN 2.0 slave node if the master node also contains all functionality of a LIN 2.0 master node, e.g. obsolete functions like Assign frame Id.

A LIN 2.1 slave node can be used in a cluster with a LIN 2.0 master node if the LIN 2.1 slave node is pre-configured, i.e. the LIN 2.1 slave node has a valid configuration after reset. A LIN 2.0 slave node shall not use NAD 0x7E since it is reserved as functional address for diagnostics in LIN2.1. The LIN 2.1 slave node will consider NAD 0x7E as a functional NAD and a LIN 2.0 slave node as a NAD.

The LIN physical layer of Revision 2.1 is technically identical to Revision 2.0. Only ambiguous and incorrect specifications have been clarified and missing specifications have been added. For example: A chapter about the physical layer compatibility has been added.

The ambiguous term "clock tolerance" has been changed into "bit rate tolerance". The constraint for slave-to-slave communication has been clarified. A chapter has been added, which specifies the bit sample timing of byte fields. The supply voltage reference has become unique. In this context the voltage reference of the battery and ground shift has been changed from the voltage across the vehicle battery connectors to the ECU supply voltage connectors.

A chapter about the performance in non-operation range has been added. A chapter about the performance during fault modes has been added. All parameters in this specification are defined for the ambient temperature range.

What is the difference between LIN and J2602?
Generally speaking, SAE J2602 is a sub set of LIN Bus Specification Revision 2.0.

SAE J2602 uses LIN experience and LIN standard. Some differences of SAE J2602 to LIN 2.0/2.1 are SAE J2602 has more stringent requirements on Sample Point conformance testing, the configuration process is different and driver status is added to each response providing additional information. On the other hand, SAE J2602 uses one fixed baud rate of 10.4kBaud only.

Where can I find more information about LIN?
Go to www.lin-subbus.de

Where can I get software libraries for LIN Data Link Layer?
Microchip provides application notes free of charge for 8-bit MCUs and 16-bit MCUs and DSCs. Several 3rd party companies also offer software libraries for Microchip MCUs and DSCs, such as Vector Informatik and Mentor Graphics.

For Microchip's software libraries, please check www.microchip.com/LIN.

How much program memory and other resources does a software library for LIN 2.0 consume?
On a PIC16F for example (AN1099A) the software driver typically uses 1636 words of program memory and 89 bytes of data memory. A 16bit Timer interrupt can be used for checking the header and response time-outs. The USART Receive Interrupt is used for receiving and back-to-back transmission bit failure checking. (An external interrupt can be used for end of Sync Break check if auto-baud feature is enabled. Note: This only necessary for older devices which have a notified errata for autobaud enable. )

Source: Microchip Technology Inc.





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