Datasheet

Figure 15-1. Reset Logic
MCU Control and Status
Register (MCUCSR)
Brown-Out
Reset Circuit
BODEN
BODLEVEL
Delay Counters
CKSEL[3:0]
CK
TIMEOUT
WDRF
BORF
EXTRF
PORF
DATA BUS
Clock
Generator
SPIKE
FILTER
Pull-up Resistor
Watchdog
Oscillator
SUT[1:0]
15.2.1 Power-on Reset
A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detection level is
defined in the table in System and Reset Characteristics. The POR is activated whenever 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.
Figure 15-2. MCU Start-up, RESET Tied to V
CC
V
RESET
TIME-OUT
INTERNAL
RESET
t
TOUT
V
POT
V
RST
CC
AVR 8-Bit Microcontroller
System Control and Reset
© 2017 Microchip Technology Inc.
Datasheet Complete
40001974A-page 60