XC886/888CLM
Serial Interfaces
User’s Manual
12-26
V1.3, 2010-02
Serial Interfaces, V 1.0
12.2
LIN
The UART module can be used to support the Local Interconnect Network (LIN) protocol
for both master and slave operations. The LIN baud rate detection feature, which
consists of the hardware logic for Break and Synch Byte detection, provides the
capability to detect the baud rate within LIN protocol using Timer 2. This allows the UART
module to be synchronized to the LIN baud rate for data transmission and reception.
Note: The LIN baud rate detection feature is available for use only with UART. To use
UART1 for LIN communication, software has to be implemented to detect the
Break and Synch Byte.
12.2.1
LIN Protocol
LIN is a holistic communication concept for local interconnected networks in vehicles.
The communication is based on the SCI (UART) data format, a single-master/multiple-
slave concept, a clock synchronization for nodes without stabilized time base. An
attractive feature of LIN is self-synchronization of the slave nodes without a crystal or
ceramic resonator, which significantly reduces the cost of hardware platform. Hence, the
baud rate must be calculated and returned with every message frame.
The structure of a LIN frame is shown in
. The frame consists of the:
•
header, which comprises a Break (13-bit time low), Synch Byte (55
H
), and ID field
•
response time
•
data bytes (according to UART protocol)
•
checksum
Figure 12-6
The Structure of LIN Frame
Each byte field is transmitted as a serial byte, as shown in
. The LSB of the
data is sent first and the MSB is sent last. The start bit is encoded as a bit with value zero
(dominant) and the stop bit is encoded as a bit with value one (recessive).
Frame slot
Frame
Response
Response
space
Header
Synch
Protected
identifier
Data 1
Data 2
Data N
Checksum
*
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