When the LP8764-Q1 device is configured to use the Watchdog Question Answer mode, the watchdog requires specific messages from the MCU in specific time intervals to detect correct operation of the MCU.

The device provides a question for the MCU in WD_QUESTION[3:0] during operation. The MCU performs a fixed series of arithmetic operations on this question to calculate the required 32-bit answer. This answer is split into four answer bytes: Answer-3, Answer-2, Answer-1, and Answer-0. The MCU writes these answer bytes one byte at a time into WD_ANSWER[7:0] from the SPI or the dedicated I²C2 interface, mapped to GPIO2 and GPIO3 pins.

A good event occurs when the MCU sends the correct answer-bytes calculated for the current question in the correct watchdog window and in the correct sequence.

A bad event occurs when one of the events that follows occur:

• The MCU sends the correct answer-bytes, but not in the correct watchdog window.
• The MCU sends incorrect answer-bytes.
• The MCU returns correct answer-bytes, but in the incorrect sequence.

If the MCU stops providing answer-bytes for the duration of the watchdog time-period, the watchdog detects a time-out event. This time-out event sets the WD_TIMEOUT status bit, increments the WD_FAIL_CNT[3:0] counter, and starts a new watchdog sequence.