12. WDOG - Watchdog Timer
0 1 2 3
4
Timeout period
Counter value
Time
Watchdog clear
System reset
Quick Facts
What?
The WDOG (Watchdog Timer) resets the system in
case of a fault condition, and can be enabled in all
energy modes as long as the low frequency clock
source is available.
Why?
If a software failure or external event renders the
MCU unresponsive, a Watchdog timeout will reset
the system to a known, safe state.
How?
An enabled Watchdog Timer implements a configu-
rable timeout period. If the CPU fails to re-start the
Watchdog Timer before it times out, a full system re-
set will be triggered. The Watchdog consumes insig-
nificant power, and allows the device to remain safe-
ly in low energy modes for up to 256 seconds at a
time.
12.1 Introduction
The purpose of the watchdog timer is to generate a reset in case of a system failure to increase application reliability. The failure can be
caused by a variety of events, such as an ESD pulse or a software failure.
12.2 Features
• Clock input from selectable oscillators
• Internal 32 kHz RC oscillator
• Internal 1 kHz RC oscillator
• External 32.768 kHz XTAL oscillator
• Configurable timeout period from 9 to 256k watchdog clock cycles
• Individual selection to keep running or freeze when entering EM2 DeepSleep or EM3 Stop
• Selection to keep running or freeze when entering debug mode
• Selection to block the CPU from entering Energy Mode 4
• Selection to block the CMU from disabling the selected watchdog clock
• Configurable warning interrupt at 25%,50%, or 75% of the timeout period
• Configurable window interrupt at 12.5%,25%,37.5%,50%,62.5%,75%,87.5% of the timeout period
• Timeout interrupt
• PRS as a watchdog clear
• Interrupt for the event where a PRS rising edge is absent before a software reset
12.3 Functional Description
The watchdog is enabled by setting the EN bit in WDOGn_CTRL. When enabled, the watchdog counts up to the period value config-
ured through the PERSEL field in WDOGn_CTRL. If the watchdog timer is not cleared to 0 (by writing a 1 to the CLEAR bit in
WDOGn_CMD) before the period is reached, the chip is reset. If a timely clear command is issued, the timer starts counting up from 0
again. The watchdog can optionally be locked by writing the LOCK bit in WDOGn_CTRL. Once locked, it cannot be disabled or recon-
figured by software.
When the EN bit in WDOGn_CTRL is cleared to 0, the watchdog counter is reset.
EFM32JG1 Reference Manual
WDOG - Watchdog Timer
silabs.com
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