Datasheet

ATmega48/88/168 Automotive [DATASHEET]
7530K–AVR–07/14
42
When the BOD is enabled, and V
CC
decreases to a value below the trigger level (V
BOT-
in Figure 8-5), the brown-out reset is
immediately activated. When V
CC
increases above the trigger level (V
BOT+
in Figure 8-5), 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
CC
if the voltage stays below the trigger level for longer than t
BOD
given in
Table 8-1 on page 40.
Figure 8-5. Brown-out Reset During Operation
8.6 Watchdog System 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 Section 8.9 “Watchdog Timer” on page 44 for details on
operation of the watchdog timer.
Figure 8-6. Watchdog System Reset During Operation
V
BOT-
V
BOT+
t
TOUT
V
CC
RESET
INTERNAL
RESET
TIME-OUT
1 CK Cycle
V
CC
RESET
INTERNAL
RESET
RESET
Time-OUT
WDT
TIME-OUT
t
TOUT