Rainbow-electronics ATmega64L Manuel d'utilisateur télécharger pdf (Page 37)

ATmega16(L)

2466B–09/01

Figure 18. External Reset During Operation

Brown-out Detection ATmega16 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 fuse BODLEVEL to be 2.7V (BODLEVEL unprogrammed),

or 4.0V (BODLEVEL programmed). The trigger level has a hysteresis to ensure spike

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

BOT+

= V

BOT

+ V

HYST

/2 and V

BOT-

= V

BOT

- V

HYST

/2.

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

BOT-

in Figure 19), the Brown-out Reset is immediately activated. When V

increases

above the trigger level (V

BOT+

in Figure 19), 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 Table 15.

Figure 19. Brown-out Reset During Operation

RESET

TIME-OUT

INTERNAL

RESET

BOT-

BOT+

TOUT

1 2 ... 32 33 34 35 36 37 38 39 40 41 42 ... 297 298

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Rainbow-electronics ATmega64L Manuel d'utilisateur Page 37

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