RXD is the interface to the processors LIN protocol controller or SCI and UART, 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. This device architecture allows the device to be used with 3.3 V and 5 V I/O processors. The RXD pin is a push-pull buffer and as such an external pull-up is not needed. In restart mode, the RXD pin is driven high. When V_CC > UV_CC for t_{RSTN_act}, the device automatically transitions to standby mode causing RXD is then pulled low to indicate a wake-up request. The RXD pin can be programmed to toggle low or high to indicate a wake up request with a pulse width of t_TOGGLE, see Figure 7-6 as an example of this feature.