Rev. 1.10

11 of �5

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��-bit �RM Co�tex™-M� MCU

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Watchdog Timer

The Watchdog Timer is a hardware timing circuitry that can be used to detect system failures due

to software malfunctions. It includes a 12-bit down-counting counter, a prescaler, a WDT counter

value register, a WDT delta value register, interrupt related circuits, WDT operation control

circuitry and the WDT protection mechanism. The Watchdog Timer can be operated in an interrupt

mode or a reset mode. The Watchdog Timer will generate an interrupt or a reset when the counter

counts down and reaches a zero value. If the software does not reload the counter value before

the Watchdog Timer underflow occurs, an interrupt or a reset will be generated when the counter

underflows. In addition, an interrupt or reset is also generated if the software reloads the counter

when the counter value is greater than or equal to the WDT delta value. That means the counter

must be reloaded within a limited timing window using a specific method. The Watchdog Timer

counter can be stopped while the processor is in the debug mode. The register write protection

function can be enabled to prevent it from changing the configuration of the Watchdog Timer

unexpectedly.

Real Time Clock

The Real Time Clock, RTC, circuitry includes the APB interface, a 32-bit up-counter, a control

register, a prescaler, a compare register and a status register. Most of the RTC circuits are located

domain. Therefore, it is necessary to be isolated from the ISO signal that comes from the power

mode. The RTC counter is used as a wakeup timer to generate a system resume from the

Power-Down mode.