ATMEGA644A-AU Atmel, ATMEGA644A-AU Datasheet - Page 53

• Manufacturer Part Number: ATMEGA644A-AU
• Description: IC MCU AVR 64K FLASH 44TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644A-AU

• 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): 1.8 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

10.1.3
8272A–AVR–01/10
External Reset
Figure 10-2. MCU Start-up, RESET Tied to V
Figure 10-3. MCU Start-up, RESET Extended Externally
An External Reset is generated by a low level on the RESET pin. Reset pulses longer than the
minimum pulse width (see
reset, even if the clock is not running. Shorter pulses are not guaranteed to generate a reset.
When the applied signal reaches the Reset Threshold Voltage – V
delay counter starts the MCU after the Time-out period – t
Figure 10-4. External Reset During Operation
164A/164PA/324A/324PA/644A/644PA/1284/1284P
INTERNAL
INTERNAL
TIME-OUT
TIME-OUT
RESET
RESET
RESET
RESET
V
V
CC
CC
CC
V
V
”System and Reset Characteristics” on page
V
POT
POT
RST
t
TOUT
CC
V
RST
t
TOUT
TOUT
– has expired.
RST
– on its positive edge, the
335) will generate a
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