
50
7674F–AVR–09/09
ATmega164P/324P/644P
Figure 9-1.
Reset Logic
9.0.3
Power-on Reset
A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detection level
V
CC is below the detection level. The POR circuit can be used to trigger the start-up Reset, as
well as to detect a failure in supply voltage.
A Power-on Reset (POR) circuit ensures that the device is reset from Power-on. Reaching the
Power-on Reset threshold voltage invokes the delay counter, which determines how long the
device is kept in RESET after V
CC rise. The RESET signal is activated again, without any delay,
when V
CC decreases below the detection level.
MCU Status
Register (MCUSR)
Brown-out
Reset Circuit
BODLEVEL [2..0]
Delay Counters
CKSEL[3:0]
CK
TIMEOUT
WDRF
BORF
EXTRF
PORF
DATA BUS
Clock
Generator
SPIKE
FILTER
Pull-up Resistor
JTRF
JTAG Reset
Register
Watchdog
Oscillator
SUT[1:0]
Power-on Reset
Circuit