ZHCSKK3B December 2019 – February 2022 TPS6594-Q1
PRODUCTION DATA
A question and answer are defined as follows:
The watchdog provides the question to the MCU when the MCU reads the WD_QUESTION[3:0] bits.
The MCU can request each new question at the start of the watchdog sequence, but this is not required to calculate the answer. The MCU can also have a software implementation, which generates the question according the circuit shown in Figure 8-26. Nevertheless, the answer and therefore the answer-bytes are always based on the question generated inside the watchdog of the device. So, if the MCU generates an incorrect question and gives answer-bytes calculated from this incorrect question, the watchdog detects a bad event
The watchdog receives an answer-byte when the MCU writes to the WD_ANSWER[7:0] bits. For each question, the watchdog requires four correct answer-bytes from the MCU in the correct timing and order (Answer-3, Answer-2, and Answer-1 in Window 1 in the correct sequence, and Answer-0 in Window 2) to detect a good event.
The watchdog sequence in Q&A mode ends after the MCU writes the fourth answer byte (Answer-0), or after a time-out event when the Window-2 time-interval elapses.