LIN Master/Slave Mode

The LIN Master mode includes capabilities to generate Slave processes. The Master process stops at the PID transmission. Any data that is transmitted in Master/Slave mode is done as a Slave process. LIN Master/Slave mode is configured by the following settings:

MODE = 1100
TXEN = 1
RXEN = 1
UxBRG = Value to achieve desired baud rate
TXPOL = 0 (for high Idle state)
STP = desired Stop bits selection
C0EN = desired Checksum mode
RxyPPS = TX pin selection code
TX pin TRIS control = 0
ON = 1

Important: The TXEN bit must be set before the Master process is received and remain set while in LIN mode whether or not the Slave process is a transmitter.

The Master process is started by writing the PID to the UxP1L register when UxP2 is ‘0’ and the UART is Idle. The UxTXIF will not be set in this case. Only the six Least Significant bits of UxP1L are used in the PID transmission.

The two Most Significant bits of the transmitted PID are PID parity bits. PID[6] is the exclusive-or of PID bits 0, 1, 2, and 4. PID[7] is the inverse of the exclusive-or of PID bits 1, 3, 4, and 5.

The UART hardware calculates and inserts these bits in the serial stream.

Writing UxP1L automatically clears the UxTXCHK and UxRXCHK registers and generates the Break, the delimiter bit, the Sync character (55h), and the PID transmission portion of the transaction. The data portion of the transaction that follows, if there is one, is a Slave process. See LIN Slave Mode for more details of that process. The master receives its own PID if RXEN is set. Software performs the Slave process corresponding to the PID that was sent and received. Attempting to write UxP1L before an active Master process is complete will not succeed. Instead, the TXWRE bit will be set.