WDT (Watch Dog Timer) is a component of MCU, which is of great significance in the debugging and running of MCU programs. Its main function is in the event of software failure, by making the device reset (if the software did not clear the device zero) to reset the single-chip microcomputer. It can also be used to wake devices from hibernation or idle mode.

Watchdog timer works

When enabled, the WDT increases until it overflows, or "timeout." Unless in hibernation or idle mode, the WDT timeout forces the device to reset. To avoid WDT time out reset, users must regularly clear watchdog timers with PWRSAV or CLRWDT instructions. If the WDT times out in hibernation or idle mode, the device wakes up and continues to execute code from the PWRSAV instruction execution point. In both cases, the WDTO bit (RCON<4>) is set to 1, indicating that the device reset or wake event is caused by the WDT timeout. If WDT wakes up the CPU from hibernation or idle mode, the "hibernation" bit (RCON<3>) or "idle" bit (RCON<2>) will also be set to 1, indicating that the device is in power-saving mode before.

Watchdog timer function works

WDT (Watch Dog Timer) is a component of MCU, which is of great significance in the debugging and running of MCU programs. Its main function is in the event of software failure, by making the device reset (if the software did not clear the device zero) to reset the single-chip microcomputer. It can also be used to switch the device from a dormant or idle mode watchdog timer to provide an independent protection system for the microcontroller. In case of a system failure, the watchdog will respond with a RESET signal after the optional timeout period, such as the x25045, which has an optional timeout period of 1.4 seconds, 600 milliseconds and 200 milliseconds. When your program crashes, the x25045 resets the MCU.

Most watchdog timers IC produce a single, limited output pulse duration when the watchdog times out. This is suitable for triggering reset or interrupt microprocessors, but some applications require a latch that outputs (fault indicator lights).

Considering the safety problem, the automobile electronic system needs the monitoring circuit to monitor the fault tolerance or safety. Watchdog timers are ideal for this type of demand by detecting, detecting, or detecting periodic pulses generated by microcontrollers under normal operating conditions. C, which can be immediately switched to the backup/redundant system in case of failure. Wake up. > watchdog timer operation

During normal operation, a WDT timeout overflow will result in a device reset. If the device is dormant, a WDT timeout overflow will wake the device to resume normal operation (known as WDT wake). Setting a bit reset on WDTE can permanently close the WDT.

The post divider assignment is completely controlled by software, which means it can be changed at any time during program execution.

To avoid unpredictable device reset, the following sequence of instructions must be executed when the allocation of the Timer0 predivider is changed to that of the WDT post-divider. This sequence of instructions is executed even if WDT is disabled.