Rainbow-electronics ATtiny861_V Manual de usuario descargar pdf (Pagina 41)

2588B–AVR–11/06

ATtiny261/461/861

Figure 9-4. External Reset During Operation

9.0.5 Brown-out Detection

ATtiny261/461/861 has an On-chip Brown-out Detection (BOD) circuit for monitoring the V

level during operation by comparing it to a fixed trigger level. The trigger level for the BOD can

be selected by the BODLEVEL Fuses. The trigger level has a hysteresis to ensure spike free

Brown-out Detection. The hysteresis on the detection level should be interpreted as V

BOT+

BOT

+ V

HYST

/2 and V

BOT-

= V

BOT

- V

HYST

/2.

When the BOD is enabled, and V

decreases to a value below the trigger level (V

BOT-

in Figure

9-5), the Brown-out Reset is immediately activated. When V

increases above the trigger level

BOT+

in Figure 9-5), the delay counter starts the MCU after the Time-out period t

TOUT

has

expired.

The BOD circuit will only detect a drop in V

if the voltage stays below the trigger level for

longer than t

BOD

given in ”System and Reset Characteristics” on page 189.

Figure 9-5. Brown-out Reset During Operation

9.0.6 Watchdog Reset

When the Watchdog times out, it will generate a short reset pulse of one CK cycle duration. On

the falling edge of this pulse, the delay timer starts counting the Time-out period t

TOUT

. Refer to

page 42 for details on operation of the Watchdog Timer.

RESET

TIME-OUT

INTERNAL

RESET

BOT-

BOT+

TOUT

1 2 ... 36 37 38 39 40 41 42 43 44 45 46 ... 235 236

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Rainbow-electronics ATtiny861_V Manual de usuario Pagina 41

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