During normal mode, if TXD is inadvertently driven permanently low by a hardware or software application failure, the LIN bus is protected by the dominant state timeout timer. This timer is triggered by a falling edge on the TXD pin. If the low signal remains on TXD for longer than t_{TXD_DTO}, the transmitter is disabled, thus allowing the LIN bus to return to recessive state and communication to resume on the bus. The protection is cleared and the t_{TXD_DTO} timer is reset by a rising edge on TXD. The TXD pin has an internal pull-up to make sure the device fails to a known recessive state if TXD is disconnected. During this fault, the transceiver remains in normal mode (assuming no change of stated request on EN), the RXD pin reflects the LIN bus and the LIN bus pull-up termination remains on. The TLIN1431x-Q1 can turn off TXD dominant state timeout when in SPI mode by using register 8'h1D[5] = 1b.