While the LIN driver is in active mode a TXD DTO circuit prevents the local node from blocking network communication in event of a hardware or software failure where TXD is held dominant longer than the time-out period t_{TXD_DTO}. The TXD DTO circuit is triggered by a falling edge on TXD. If no rising edge is seen before the time-out constant of the circuit, t_{TXD_DTO}, expires the LIN driver is disabled releasing the bus line to the recessive level. This keeps the bus free for communication between other nodes on the network. The LIN driver is re-activated on the next dominant to recessive transition on the TXD terminal, thus clearing the dominant time-out. During this fault, the transceiver remains in normal mode, the integrated LIN bus pull-up termination remains on, and the LIN receiver and RXD terminal remain active reflecting the LIN bus data.

The TXD pin has an internal pull-down to ensure the device fails to a known state if TXD is disconnected. If EN pin is high at power-up, the TLIN1021A-Q1 enters normal mode. With the internal TXD connected low, the DTO timer starts. To avoid a t_{TXD_DTO} fault, a recessive signal should be put onto the TXD pin before the t_{TXD_DTO} timer expires, or the device should be into sleep mode by connecting EN pin low.