ATMEGA128A-AN Atmel, ATMEGA128A-AN Datasheet - Page 51

• Manufacturer Part Number: ATMEGA128A-AN
• Description: IC MCU AVR 128K FLASH 64TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA128A-AN

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: EBI/EMI, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 128KB (64K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 4K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-TQFP
• Core: AVR8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

10. System Control and Reset
10.1
10.2
8151H–AVR–02/11
Resetting the AVR
Reset Sources
During Reset, all I/O registers are set to their initial values, and the program starts execution
from the Reset Vector. The instruction placed at the Reset Vector must be a JMP – absolute
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. The circuit diagram in
logic. The the electrical parameters of the reset circuitry are defined in
acteristics” on page
The I/O ports of the Atmel
goes active. This does 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 CKSEL fuses. The different selec-
tions for the delay period are presented in
The ATmega128A has five sources of reset:
• Power-on Reset. The MCU is reset when the supply voltage is below the Power-on Reset
• External Reset. The MCU is reset when a low level is present on the RESET pin for longer
• Watchdog Reset. The MCU is reset when the Watchdog Timer period expires and the
• Brown-out Reset. The MCU is reset when the supply voltage V
• JTAG AVR Reset. The MCU is reset as long as there is a logic one in the Reset Register, one
threshold (V
than the minimum pulse length.
Watchdog is enabled.
Reset threshold (V
of the scan chains of the JTAG system. Refer to the section
scan” on page 255
POT
).
324.
BOT
for details.
) and the Brown-out Detector is enabled.
®
AVR
®
are immediately reset to their initial state when a reset source
“Clock Sources” on page
“IEEE 1149.1 (JTAG) Boundary-
CC
Figure 10-1
39.
is below the Brown-out
ATmega128A
“System and Reset Char-
shows the reset
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