LIN master is available with the following configuration:
- LIN master format (CTRLA.FORM = 0x02)
- Asynchronous mode (CTRLA.CMODE = 0)
- 16x sample rate using fractional baud rate generation (CTRLA.SAMPR = 1)
LIN frames start with a header transmitted by the master. The header consists of the break, sync, and identifier fields. After the master transmits the header, the addressed slave will respond with 1-8 bytes of data plus checksum.
Using the LIN command field (CTRLB.LINCMD), the complete header can be automatically transmitted, or software can control transmission of the various header components.
When CTRLB.LINCMD=0x1, software controls transmission of the LIN header. In this case, software uses the following sequence.
- CTRLB.LINCMD is written to 0x1.
- DATA register written to 0x00. This triggers transmission of the break field by hardware. Note that writing the DATA register with any other value will also result in the transmission of the break field by hardware.
- DATA register written to 0x55. The 0x55 value (sync) is transmitted.
- DATA register written to the identifier. The identifier is transmitted.
When CTRLB.LINCMD=0x2, hardware controls transmission of the LIN header. In this case, software uses the following sequence.
- CTRLB.LINCMD is written to 0x2.
- DATA register written to the identifier. This triggers transmission of the complete header by hardware. First the break field is transmitted. Next, the sync field is transmitted, and finally the identifier is transmitted.
In LIN master mode, the length of the break field is programmable using the break length field (CTRLC.BRKLEN). When the LIN header command is used (CTRLB.LINCMD=0x2), the delay between the break and sync fields, in addition to the delay between the sync and ID fields are configurable using the header delay field (CTRLC.HDRDLY). When manual transmission is used (CTRLB.LINCMD=0x1), software controls the delay between break and sync.
After header transmission is complete, the slave responds with 1-8 data bytes plus checksum.