Sync Break
Sync Field
ID Field
Checksum
Master Header
N Data Fields Response
Extended Frame With Embedded Checksum Bytes
In-frame space
Checksum
Checksum
LIN Communication Formats
1258
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Serial Communication Interface (SCI)/ Local Interconnect Network (LIN)
Module
If the synch field is not detected within the given tolerances, the inconsistent-synch-field-error (ISFE) flag
will be set. An ISFE interrupt will be generated, if enabled by its respective bit in the SCISETINT register.
The ID byte should be received after the synch field validation was successful. Any time a valid break
(larger than 11 T
bit
) is detected, the receiver’s state machine should reset to reception of this new frame.
This reset condition is only valid during response state, not if an additional synch break occurs during
header reception.
NOTE:
When an inconsistent synch field (ISFE) error occurs, suggested action for the application is
to reset the SWnRST bit and set the SWnRST bit to make sure that the internal state
machines are back to their normal states
25.7.6 Extended Frames Handling
The LIN protocol 2.0 and prior includes two extended frames with identifiers 62 (user defined) and 63
(reserved extended). The response data length of the user-defined frame (ID 62, or 0x3E) is unlimited.
The length for this identifier will be set at network configuration time to be shared with the LIN bus nodes.
Extended frame communication is triggered on reception of a header with identifier 0x3E; see
. Once the extended frame communication is triggered, unlike normal frames, this communication
needs to be stopped before issuing another header. To stop the extended frame communication the
STOP EXT FRAME bit must be set.
Figure 25-19. Optional Embedded Checksum in Response for Extended Frames
An ID interrupt will be generated (if enabled and there is a match) on reception of ID 62 (0x3E). This
interrupt allows the CPU using a software counter to keep track of the bytes that are being sent out and
decides when to calculate and insert a checksum byte (recommended at periodic rates). To handle this
procedure, SC bit is used. A write to the send checksum bit SC will initiate an automatic send of the
checksum byte. The last data field should always be a checksum in compliance with the LIN protocol.
The periodicity of the checksum insertion, defined at network configuration time, is used by the receiving
node to evaluate the checksum of the ongoing message, and has the benefit of enhanced reliability.
For the sending node, the checksum is automatically embedded each time the send checksum bit SC is
set. For the receiving node, the checksum is compared each time the compare checksum bit CC is set;
see
.
NOTE:
The LIN 2.0 enhanced checksum does not apply to the reserved identifiers. The reserved
identifiers always use the classic checksum.
