LIN Slave Mode

The LIN Slave mode is configured by the following settings:

• MODE = 1011
• TXEN = 1
• RXEN = 1
• UxP2 = Number of data bytes to transmit
• UxP3 = Number of data bytes to receive
• UxBRG = Value to achieve default 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

The Slave process starts upon detecting a Break on the RX pin. The Break clears the UxTXCHK, UxRXCHK, UxP2, and UxP3 registers. At the end of the Break, the auto-baud circuity is activated and the baud rate is automatically set using the Sync character following the Break. The character following the Sync character is received as the PID code and is saved in the receive FIFO. The UART computes the two PID parity bits from the six Least Significant bits of the PID. If either parity bit does not match the corresponding bit of the received PID code, the PERIF flag is set and saved at the same FIFO location as the PID code. The UxRXIF bit is set indicating that the PID is available.

Software retrieves the PID by reading the UxRXB register and determines the Slave process to execute from that. The checksum method, number of data bytes, and whether to send or receive data, is defined by software according to the PID code.