Rainbow-electronics ATmega8515L Manual do Utilizador descarregar pdf (Página 46)

ATmega8515(L)

2512A–AVR–04/02

Watchdog Reset When the Watchdog times out, it will generate a short reset pulseof one CK cycle dura-

tion. Onthe falling edge of thispulse, the delay timerstartscounting theTime-out period

TOUT

.Refer to page 50 fordetails on operation of the Watchdog Timer.

Figure 26. Watchdog Reset During Operation

MCU Control and Status

The MCU Control andStatus Registerprovides information on which reset source

caused an MCU Reset.

• Bit 3 – WDRF: Watchdog Reset Flag

Thisbit isset if a Watchdog Reset occurs.The bit isreset by aPower-on Reset, orby

writing a logiczerotothe flag.

• Bit 2 – BORF: Brown-out Reset Flag

Thisbit isset if a Brown-out Reset occurs.The bit isreset by aPower-on Reset, orby

writing a logiczerotothe flag.

• Bit1–EXTRF: External Reset Flag

Thisbit isset if an External Reset occurs.The bit isreset by aPower-on Reset, orby

writing a logiczerotothe flag.

• Bit 0 – PORF: Power-on Reset Flag

Thisbit isset if aPower-on Reset occurs.The bit isreset only by writing a logiczeroto

the flag.

To makeuseof the reset flags to identify a reset condition, theusershould read and

then reset the MCUCSRas early aspossibleinthe program. If the register iscleared

before anotherreset occurs, the sourceof the reset can be foundbyexamining the reset

flags.

Bit 76543 210

– – SM2 –WDRFBORFEXTRF PORF MCUCSR

Read/Write R/W R/W RR/W R/W R/W R/W R/W

Initial Value000 See Bit Description

1 2 ... 41 42 43 44 45 46 47 48 49 50 51 ... 222 223

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Rainbow-electronics ATmega8515L Manual do Utilizador Página 46