LIN lower layers
The LIN data link layer, often called the LIN protocol, specifies a commander-responder protocol. The LIN Commander uses one or more pre-programmed scheduling tables to start the sending and receiving to the LIN frames. These scheduling tables contain at least the relative timing, when the LIN frame sending is initiated. The LIN frame consists of two parts: header and response. The LIN Commander sends the header, while either one dedicated LIN Responder or the LIN Commander itself transmits the response.
The header comprises the 1-byte Break, the Inter-Byte Space, the 1-byte SYNC (5516), the Identifier, and the Response Space. The responses consist of the payload-bytes and the CRC byte.
Transmitted data within the LIN frame is transmitted serially as 8-bit data-bytes with one additional start bit, one additional stop-bit, but no parity bit. Note that the break field in the header has no start bit and no stop bit.
Bit rates may vary within the range of 1 kbit/s to 20 kbit/s. Bit values on the bus are recessive (logical high) or dominant (logical low). The time normal is considered by the LIN Commanders stable clock source, the smallest entity is one bit time (52 µs at a bitrate of 19,2 kbit/s). Two bus states are defined: sleep mode and active mode. While data is on the bus, all LIN-nodes are requested to be in active mode. After a specified timeout, the nodes enter the sleep mode and are released back to active mode by a wake-up frame. This frame may be sent by any node requesting activity on the bus, either the LIN Commander following its internal schedule, or one of the attached LIN Responders being activated by its internal software application. After all nodes are awakened, the LIN Commander continues to schedule the next LIN frame.
For more technical information on LIN you may visit LIN on Wikipedia.
Auto addressing methods
In the informative Annex C of ISO 17987-3, there are IDs assigned for different auto addressing methods.
Here you find descriptions of the methods:
| ID | Method name | Company |
|---|---|---|
| 0x01 | Extra Wide Daisy Chain | NXP |
| 0x02 | Bus Shunt Method 1 | Elmos |
| 0x03 | LIN Switch Method | NXP |
| 0x04 | Low'R auto-addressing | Hartzsch |
| 0xF1 | Bus Shunt Method 2 | Elmos |
| 0xF2 | Bus direction method | Infineon |