RXD is the interface to the processor's LIN protocol controller, which reports the state of the LIN bus voltage. LIN recessive (near V_SUP) is represented by a high level on the RXD and LIN dominant (near ground) is represented by a low level on the RXD pin. The RXD output structure is an open-drain output stage. This allows the device to be used with 3.3 V and 5 V_I/O processors. If the processor's RXD pin does not have an integrated pull-up, an external pull-up resistor to the processors I and O supply voltage is required. In standby mode, the RXD pin is driven low to indicate a wake-up request from the LIN bus from sleep mode. When going from normal mode to standby mode, the RXD pin is released and pulled-up to the voltage rail that the external pull-up resistor is connected. A LIN bus wake event will cause the RXD pin to be pulled low indicating a wake request.