STR720 datasheet(303/401 Pages) STMICROELECTRONICS

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STR720 - WATCHDOG TIMER (WDG)

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20 WATCHDOG TIMER (WDG)

20.1 Introduction

The Watchdog Timer peripheral can be used as free-running timer or as Watchdog to resolve

STR720 microcontroller malfunctions due to hardware or software failures.

20.2 Main Features

■

16-bit down Counter

■

8-bit clock Prescaler

■

Safe Reload Sequence

■

Free-running Timer mode

■

End of Counting interrupt generation

■

Second clock source (4 kHz derived from 32 kHz RTC clock

20.3 Functional Description

Figure 42 shows the functional blocks of the Watchdog Timer module. The module can work

as Watchdog or as Free-running Timer. In both working modes the 16-bit Counter value can

be accessed through a reading of the WDTCNT register.

20.3.1

Free-running Timer mode

If the WE bit of WDTCR register is not written to ‘1’ by software, the peripheral enter in

Free-running Timer mode. When in this operating mode as the SC bit of WDTCR register is

written to ‘1’ the WDTVR value is loaded in the Counter and the Counter starts counting down.

Figure 42. Watchdog Timer Functional Block

EOC

APB_CLK

IRQ /

ECM

16-bit Counter

WDTVR Register

CLK_AF/8

8-bit Prescaler

WDTPR Register

SYS RST

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