SLLSFU1A December 2023 – July 2024 MCF8315C
PRODMIX
MCF8315C provides an external watchdog feature - EXT_WDT_EN bit should be set to 1b to enable the external watchdog. When this feature is enabled, the device waits for a tickle (low to high transition in EXT_WD pin, WATCHDOG_TICKLE set to 1b in I2C mode) from the external watchdog input for a configured time interval; if the time interval between two consecutive tickles is higher than the configured time, a watchdog fault is triggered. This fault can be configured using EXT_WDT_FAULT_MODE either as a report only fault or as a latched fault with outputs in Hi-Z state. The latched fault can be cleared by writing 1b to CLR_FLT. When a watchdog timeout occurs, WATCHDOG_FAULT bit is set to 1b. In case, the next tickle arrives before the configured time interval elapses, the watchdog timer is reset and it begins to wait for the next tickle. This can be used to continuously monitor the health of an external MCU (which is the external watchdog input) and put the MCF8315C outputs in Hi-Z in case the external MCU is in a fault/hang state.
The external watchdog input is selected using EXT_WDT_INPUT_MODE and can either be the EXT_WD pin or the I2C interface. The time interval between two tickles to trigger a watchdog fault is configured by EXT_WDT_CONFIG; there are 4 time settings - 100, 200, 500 and 1000ms for the EXT_WD pin based watchdog and 4 time settings - 1, 2, 5 and 10s for the I2C based watchdog.