ATMEGA32A_1 Datasheet, PDF (41/352 Pages) ATMEL Corporation – 8-bit Microcontroller with 32K Bytes In-System Programmable Flash

ATmega32A
Figure 10-5. Brown-out Reset During Operation
V_CC
V_BOT-
RESET
V_BOT+
TIME-OUT
t_TOUT
INTERNAL
RESET
10.2.4
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
“Watchdog Timer” on page 42 for details.
Figure 10-6. Watchdog Reset During Operation
CC
CK
10.3
Internal Voltage Reference
ATmega32A features an internal bandgap reference. This reference is used for Brown-out
Detection, and it can be used as an input to the Analog Comparator or the ADC. The 2.56V ref-
erence to the ADC is generated from the internal bandgap reference.
10.3.1
Voltage Reference Enable Signals and Start-up Time
The voltage reference has a start-up time that may influence the way it should be used. The
start-up time is given in “System and Reset Characteristics” on page 299. To save power, the
reference is not always turned on. The reference is on during the following situations:
1. When the BOD is enabled (by programming the BODEN Fuse).
2. When the bandgap reference is connected to the Analog Comparator (by setting the
ACBG bit in ACSR).
3. When the ADC is enabled.
Thus, when the BOD is not enabled, after setting the ACBG bit or enabling the ADC, the user
must always allow the reference to start up before the output from the Analog Comparator or
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