5.12.1 WATCHDOG BEHAVIOR DURING POWER-ON AND AFTER MCU RESET

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For a safe start-up, the microcontroller must issue a watchdog trigger command, followed by the configuration of the watchdog via the WDCR registers. Following this, the device enters Device Standby mode. As soon as the ATA6847 enters Standby mode, the watchdog starts with a long open window (t_LW). Within this long open window, the watchdog must be triggered. If the watchdog trigger is missing, the watchdog will generate a Reset via the NRES pin. In case of a correct first trigger within the long open window time, the watchdog starts its normal operation.

The watchdog cannot be disabled and configured in the following cases:

After the power-on of the device and before it receives the first trigger in Long Open Window mode.
In all other cases when the watchdog is enabled and the device moves from MCU Reset mode to Standby mode, before the watchdog receives the first trigger.

If the WDLW bit from the Watchdog Control Register 1 is set to ‘1’ (default value), the watchdog timer will always be reset when the Reset pulse time expires and starts the long open window after the device enters Standby mode. Otherwise, the watchdog will continue with its normal operation immediately and skip the long window.