The watchdog sequence events are as follows for the different scenarios listed:

• A good event occurs when all answer bytes are correct in value and timing. After such a good event, following events occur:
  1. The WD_FAIL_CNT[2:0] counter decrements by one at the end of the watchdog-sequence.
  2. The question-counter increments by one and the watchdog generates a new question.
• A bad event occurs when all answer-bytes are correct in value but not in correct timing. After such a bad event, following events occur:
  1. The WD_SEQ_ERR and WD_BAD_EVENT status bits are set if Window-1 time-interval elapses before watchdog has received Answer-3, Answer-2 and Answer-1.
  2. The WD_ANSW_EARLY and WD_BAD_EVENT status bits are set if watchdog receives all four answers in Window-1.
  3. The WD_FAIL_CNT[2:0] counter increments by one at the end of the watchdog-sequence.
  4. The question-counter does not change, and hence the watchdog does not generate a new question.
• A bad event occurs when one or more of the answer-bytes are not correct in value but in correct timing. After such a bad event, following events occur:
  1. The WD_ANSW_ERR and WD_BAD_EVENT status bits are set as soon as the watchdog detects an incorrect answer-byte.
  2. The WD_FAIL_CNT[2:0] counter increments by one at the end of the watchdog-sequence.
  3. The question-counter does not change, and hence the watchdog does not generate a new question.
• A bad event occurs when one or more of the answer-bytes are not correct in value and not in correct timing. After such a bad event, following events occur:
  1. The WD_ANSW_ERR and WD_BAD_EVENT status bits are set as soon as the watchdog detects an incorrect answer-byte.
  2. The WD_SEQ_ERR and WD_BAD_EVENT status bits are set if Window-1 time-interval elapses before watchdog has received Answer-3, Answer-2 and Answer-1.
  3. The WD_ANSW_EARLY and WD_BAD_EVENT status bits are set if watchdog receives all four answer-bytes in Window-1.
  4. The WD_FAIL_CNT[2:0] counter increments by one at the end of the watchdog-sequence.
  5. The question-counter does not change, and hence the watchdog does not generate a new question.
• A time-out event occurs when the device receives less than 4 answer-bytes before Window-2 time-interval elapses. After a time-out event occurs, following events occur:
  1. WD_SEQ_ERR and WD_BAD_EVENT status bits are set if Window-1 time-interval elapses before watchdog has received Answer-3, Answer-2 and Answer-1.
  2. The WD_TIMEOUT and WD_BAD_EVENT status bits are set at the end of the watchdog-sequence.
  3. The WD_FAIL_CNT[2:0] counter increments by one at the end of the watchdog-sequence.
  4. The question-counter does not change, and hence the watchdog does not generate a new question.

The status bit WD_BAD_EVENT is read-only. The watchdog clears the WD_BAD_EVENT status bit at the end of the watchdog-sequence.

The status bits WD_SEQ_ERR, WD_ANSW_EARLY, and WD_TIMEOUT are latched until the MCU writes a ‘1’ to these bits. If one or more of these status bits are set, the watchdog can still detect a good event in the next watchdog-sequence. These status bits are read-only. The watchdog clears the WD_BAD_EVENT status bit at the end of the watchdog-sequence.

Figure 8-24 shows the flow-chart of the watchdog in Q&A mode.

Figure 8-24 Flow Chart for WatchDog in Q&A Mode