ATmega32A datasheet(41/352 Pages) ATMEL

41 / 352 page

8155B–AVR–07/09

ATmega32A

Figure 10-5. Brown-out Reset During Operation

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

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:

When the BOD is enabled (by programming the BODEN Fuse).

When the bandgap reference is connected to the Analog Comparator (by setting the

ACBG bit in ACSR).

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

VCC

RESET

TIME-OUT

INTERNAL

RESET

VBOT-

VBOT+

tTOUT

ATmega32A Datenblatt(PDF) 41 Page - ATMEL Corporation