In both Slave and Master modes, the UART module will automatically format and send/receive the proper headers and data. However, all processing of PIDs and deciding which data to send needs to be handled by application software. An example of both a basic send and receive can be found in the “LIN Master/Slave Example code using the Protocol UART" code example on MPLAB XPRESS (http://mplabxpress.microchip.com/mplabcloud/example/details/741).