Rainbow-electronics ATmega163L Manual de usuario descargar pdf (Pagina 25)

ATmega163(L)

Brown-out Detection

ATmega163 has an on-chip brown-out detection (BOD) circuit for monitoring the V

level during the operation. The BOD

circuit can be enabled/disabled by the fuse BODEN. When the BOD is enabled (BODEN programmed), and V

decreases

to a value below the trigger level, the brown-out reset is immediately activated. When V

increases above the trigger level,

the brown-out reset is deactivated after a delay. The delay is defined by the user in the same way as the delay of POR sig-

nal, in Table 5. The trigger level for the BOD can be selected by the fuse BODLEVEL to be 2.7V (BODLEVEL

unprogrammed), or 4.0V (BODLEVEL programmed). The trigger level has a hysteresis of 50 mV to ensure spike free

brown-out detection.

The BOD circuit will only detect a drop in V

if the voltage stays below the trigger level for longer than 9 µs for trigger level

4.0V, 21 µs for trigger level 2.7V (typical values).

Figure 28. Brown-out Reset During Operation

The hysteresis on V

BOT

: V

BOT+

= V

BOT

+ 25 mV, V

BOT-

= V

BOT

- 25 mV

Watchdog Reset

When the Watchdog times out, it will generate a short reset pulse of 1 XTAL cycle duration. On the falling edge of this

pulse, the delay timer starts counting the Time-out period t

TOUT

. Refer to page 51 for details on operation of the Watchdog

Timer.

Figure 29. Watchdog Reset During Operation

VCC

RESET

TIME-OUT

INTERNAL

RESET

BOT-

BOT+

TOUT

1 CK Cycle

1 2 ... 20 21 22 23 24 25 26 27 28 29 30 ... 155 156

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Rainbow-electronics ATmega163L Manual de usuario Pagina 25

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