SPRUI33H November 2015 – June 2024 TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1
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 is 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 Figure 27-19. 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.
An ID interrupt is 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 initiates an automatic send of the checksum byte. The last data field can 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 Figure 27-20.