MC9S08EL32 Datasheet, PDF (203/356 Pages) Freescale Semiconductor, Inc – 8-Bit HCS08 Central Processor Unit (CPU)

HEADER
DATA
SYNCH
BREAK
0x55
SYNCH IDENT
BYTE FIELD
DATA
FIELD
DATA
FIELD
DATA
FIELD
DATA
FIELD
DATA
FIELD
DATA
FIELD
0
1
2
3
4
5
13 OR MORE BITS (LIN 1.3)
Figure 12-13. Typical LIN MESSAGE FRAME
DATA
FIELD
6
DATA
FIELD
7
CHECKSUM
FIELD
12.6.1 LIN Message Frame Header
The HEADER section of all LIN messages is transmitted by the master node in the network and contains
synchronization data, as well as the identifier to define what information is to be contained in the message
frame. Formally, the header is comprised of three parts:
1. SYNCH BREAK
2. SYNCH BYTE (0x55)
3. IDENTIFIER FIELD
The first two components are present to allow the LIN slave nodes to recognize the beginning of the
message frame and derive the bit rate of the master module.
The SYNCH BREAK allows the slave to see the beginning of a message frame on the bus. The SLIC
module can receive a standard 10-bit break character for the SYNCH BREAK, or any break symbol 10 or
more bit times in length. This encompasses the LIN requirement of 13 or more bits of length for the
SYNCH BREAK character.
The SYNCH BYTE is always a 0x55 data byte, providing five falling edges for the slave to derive the bit
rate of the master node.
The identifier byte indicates to the slave what is the nature of the data in the message frame. This data
might be supplied from either the master node or the slave node, as determined at system design time. The
slave node must read this identifier, check for parity errors, and determine whether it is to send or receive
data in the data field.
More information on the HEADER is contained in Section 12.6.7.1, “LIN Message Headers.”
12.6.2 LIN Data Field
The data field is comprised of standard bytes (eight data bits, no parity, one stop bit) of data, from 0–8
bytes for normal LIN frames and greater than eight bytes for extended LIN frames. The SLIC module will
either transmit or receive these bytes, depending upon the user code interpretation of the identifier byte.
Data is always transmitted into the data field least significant byte (LSB) first.
The SLIC module can automatically handle up to 64 bytes in extended LIN message frames without
significantly changing program execution.
MC9S08EL32 Series and MC9S08SL16 Series Data Sheet, Rev. 3
Freescale Semiconductor
205