During Normal mode, the only mode where the CAN driver is active, the 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 CAN driver is disabled. This keeps the bus free for communication between other nodes on the network. The CAN driver is re-activated when a recessive signal is seen on the TXD terminal, thus clearing the dominant time out. The receiver and RXD terminal reflects what is on the CAN bus and the bus terminals is biased to recessive level during a TXD DTO. This fault is indicated via the TXDDTO flag shown on the nFAULT terminal.

Figure 8-1 Example Timing Diagram for TXD DTO