5.7.2 Watchdog Timer (WDT)

AVR and PIC32CM MCUs feature a Watchdog Timer (WDT) to monitor program execution and recover from software faults such as runaway or deadlocked code. The WDT operates asynchronously from a dedicated, CPU-independent clock source, ensuring it functions even if the main clock fails. Both the AVR and PIC32CM WDTs support normal and window modes, in which the WDT must be cleared within a specific time window to avoid a system reset.

Some AVR devices also include a Synchronous WDT (SWDT) in addition to the standard WDT for safety-critical applications where software functionality and sequencing failures must be detected.

Table 5-28 shows a comparison of features between AVR and PIC32CM.

Table 5-28. AVR® and PIC32CM WDT Features
Feature/AspectAVR® WDT/SWDTPIC32CM WDT
Operation

Varies per device family:

Asynchronous (WDT)

Synchronous (SWDT)

Asynchronous
Clock Source

WDT: OSC32K, 1.024 kHz

SWDT: CLK_PER

Dedicated internal oscillator
Window ModeSupportedSupported
Time-out Periods

WDT: 8 ms to 8s

SWDT: 24-bit value

Normal: 8 to 16,384 cycles

Windowed: 16 to 32,768 cycles

Early Warning InterruptSWDT: Supported Supported
Always-On CapabilitySupportedSupported
Configuration (Change) ProtectionSupportedSupported
Operation in Sleep ModesSupportedSupported
Test/Functional SafetySWDT: SupportedN/A
Reset ActionSystem reset on time-out or window violationSystem reset on time-out or window violation
Interrupt on TimeoutSWDT: SupportedSupported (early warning)