Datasheet

52
8011Q–AVR–02/2013
ATmega164P/324P/644P
Figure 8-2. MCU Start-up, RESET Tied to V
CC
Figure 8-3. MCU Start-up, RESET Extended Externally
8.4 External Reset
An External Reset is generated by a low level on the RESET pin. Reset pulses longer than the
minimum pulse width (see ”System and Reset Characteristics” on page 331) will generate a
reset, even if the clock is not running. Shorter pulses are not guaranteed to generate a reset.
When the applied signal reaches the Reset Threshold Voltage – V
RST
– on its positive edge, the
delay counter starts the MCU after the Time-out period – t
TOUT
– has expired.
Figure 8-4. External Reset During Operation
V
RESET
TIME-OUT
INTERNAL
RESET
t
TOUT
V
POT
V
RST
CC
RESET
TIME-OUT
INTERNAL
RESET
t
TOUT
V
POT
V
RST
V
CC
CC