ATMEGA644P-20AU Atmel, ATMEGA644P-20AU Datasheet - Page 50

• Manufacturer Part Number: ATMEGA644P-20AU
• Description: IC MCU AVR 64K FLASH 44-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644P-20AU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K 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: 44-TQFP, 44-VQFP
• Processor Series: ATMEGA64x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: 2-Wire, SPI, UART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 32
• Number Of Timers: 3
• Operating Supply Voltage: 4.5 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 8 channel
• A/d Inputs: 8-Channel, 10-Bit
• Cpu Speed: 20 MIPS
• Eeprom Memory: 2K Bytes
• Input Output: 32
• Interface: 2-Wire/JTAG/SPI/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 44-pin TQFP
• Programmable Memory: 64K Bytes
• Timers: 2-8-bit, 1-16-bit
• Voltage, Range: 2.7-5.5 V
• Cpu Family: ATmega
• Device Core: AVR
• Device Core Size: 8b
• Frequency (max): 20MHz
• Total Internal Ram Size: 4KB
• # I/os (max): 32
• Number Of Timers - General Purpose: 3
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 2.7V
• Instruction Set Architecture: RISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 44
• Controller Family/series: AVR MEGA
• No. Of I/o's: 32
• Eeprom Memory Size: 2KB
• Ram Memory Size: 4KB
• Rohs Compliant: Yes
• For Use With: ATSTK600-TQFP44 - STK600 SOCKET/ADAPTER 44-TQFPATSTK600-DIP40 - STK600 SOCKET/ADAPTER 40-PDIP770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAG770-1005 - ISP 4PORT FOR ATMEL AVR MCU JTAG770-1004 - ISP 4PORT FOR ATMEL AVR MCU SPIATAVRISP2 - PROGRAMMER AVR IN SYSTEM
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8. System Control and Reset
8.1
8.2
8011O–AVR–07/10
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
shows the reset logic.
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.
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 dif-
ferent selections for the delay period are presented in
The ATmega164P/324P/644P 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 than
• 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
the minimum pulse length.
Watchdog is enabled.
threshold (V
of the scan chains of the JTAG system. Refer to the section
scan” on page 266
POT
BOT
).
) and the Brown-out Detector is enabled.
for details.
”System and Reset Characteristics” on page 331
ATmega164P/324P/644P
”Clock Sources” on page
”IEEE 1149.1 (JTAG) Boundary-
CC
is below the Brown-out Reset
Figure 8-1 on page 51
defines the electrical
30.
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