Atmel ATmega328P Xplained Mini MEGA328P-XMINI MEGA328P-XMINI Ficha De Dados
Códigos do produto
MEGA328P-XMINI
48
ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]
Atmel-8271H-AVR- ATmega-Datasheet_08/2014
11.
System Control and Reset
11.1
Resetting the AVR
During reset, all I/O Registers are set to their initial values, and the program starts execution from the Reset
Vector. For ATmega168A/168PA/328/328P the instruction placed at the Reset Vector must be a JMP –
Absolute Jump – instruction to the reset handling routine. For the ATmega 48A/48PA and ATmega88A/88PA,
the instruction placed at the Reset Vector must be an RJMP – Relative Jump – instruction to the reset handling
routine. If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular
program code can be placed at these locations. This is also the case if the Reset Vector is in the Application
section while the Interrupt Vectors are in the Boot section or vice versa
(ATmega88A/88PA/168A/168PA/328/328P only). The circuit diagram in
Vector. For ATmega168A/168PA/328/328P the instruction placed at the Reset Vector must be a JMP –
Absolute Jump – instruction to the reset handling routine. For the ATmega 48A/48PA and ATmega88A/88PA,
the instruction placed at the Reset Vector must be an RJMP – Relative Jump – instruction to the reset handling
routine. If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular
program code can be placed at these locations. This is also the case if the Reset Vector is in the Application
section while the Interrupt Vectors are in the Boot section or vice versa
(ATmega88A/88PA/168A/168PA/328/328P only). The circuit diagram in
shows the
defines the electrical parameters of the reset circuitry.
The I/O ports of the AVR are immediately reset to their initial state when a reset source goes active. This does
not require any clock source to be running.
not require any clock source to be running.
After all reset sources have gone inactive, a delay counter is invoked, stretching the internal reset. This allows
the power to reach a stable level before normal operation starts. The time-out period of the delay counter is
defined by the user through the SUT and CKSEL Fuses. The different selections for the delay period are
presented in
the power to reach a stable level before normal operation starts. The time-out period of the delay counter is
defined by the user through the SUT and CKSEL Fuses. The different selections for the delay period are
presented in
11.2
Reset Sources
The ATmega48A/PA/88A/PA/168A/PA/328/P has four sources of reset:
Power-on Reset. The MCU is reset when the supply voltage is below the Power-on Reset threshold
(V
(V
POT
).
External Reset. The MCU is reset when a low level is present on the RESET pin for longer than the
minimum pulse length.
minimum pulse length.
Watchdog System Reset. The MCU is reset when the Watchdog Timer period expires and the Watchdog
System Reset mode is enabled.
System Reset mode is enabled.
Brown-out Reset. The MCU is reset when the supply voltage V
CC
is below the Brown-out Reset threshold
(V
BOT
) and the Brown-out Detector is enabled.