ATMEGA644A-PU Atmel, ATMEGA644A-PU Datasheet - Page 57

• Manufacturer Part Number: ATMEGA644A-PU
• Description: IC MCU AVR 64K FLASH 40PDIP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644A-PU

• 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: 40-DIP (0.600", 15.24mm)
• Processor Series: ATmega
• Core: AVR
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: JTAG, TWI, SPI, USART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 32
• Number Of Timers: 3
• Operating Supply Voltage: 3.3 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• Minimum Operating Temperature: - 40 C
• Operating Temperature Range: - 40 C to + 85 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8272A–AVR–01/10
1. In the same operation, write a logic one to the Watchdog change enable bit (WDCE) and
2. Within the next four clock cycles, write the WDE and Watchdog prescaler bits (WDP) as
The following code example shows one assembly and one C function for turning off the Watch-
dog Timer. The example assumes that interrupts are controlled (e.g. by disabling interrupts
globally) so that no interrupts will occur during the execution of these functions.
Note:
164A/164PA/324A/324PA/644A/644PA/1284/1284P
Assembly Code Example
C Code Example
WDE. A logic one must be written to WDE regardless of the previous value of the WDE
bit.
desired, but with the WDCE bit cleared. This must be done in one operation.
WDT_off:
void WDT_off(void)
{
}
; Turn off global interrupt
cli
; Reset Watchdog Timer
wdr
; Clear WDRF in MCUSR
in
andi
out
; Write logical one to WDCE and WDE
; Keep old prescaler setting to prevent unintentional time-out
in
ori
out
; Turn off WDT
ldi
out
; Turn on global interrupt
sei
ret
__disable_interrupt();
__watchdog_reset();
/* Clear WDRF in MCUSR */
MCUSR &= ~(1<<WDRF);
/* Write logical one to WDCE and WDE */
/* Keep old prescaler setting to prevent unintentional time-out */
WDTCSR |= (1<<WDCE) | (1<<WDE);
/* Turn off WDT */
WDTCSR = 0x00;
__enable_interrupt();
1. The example code assumes that the part specific header file is included.
r16, MCUSR
r16, ~(1<<WDRF)
MCUSR, r16
r16, WDTCSR
r16, (1<<WDCE) | (1<<WDE)
WDTCSR, r16
r16, (0<<WDE)
WDTCSR, r16
(1)
(1)
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