Microchip Technology Power Debugger Manual page 20

Important: Because this example prescales the clock to 8 MHz/64, the ISP programming clock must be
set to less than 32 kHz to be below 1/4 of the main clock when attempting to reprogram the device!
3.1.11 Using Sleep Mode
Power consumption has been reduced, but the CPU is still actively doing nothing. To benefit from an interrupt-driven
model, the CPU can be put to sleep while waiting for interrupts. In addition, we will power-down all peripherals not
used to further reduce power consumption. The code below is included in project low_power_103.
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <avr/power.h>
ISR (TIMER2_OVF_vect)
{
if (PORTB == 0x00) {
// LED is OFF, turn it on
PORTB = (1 << 5);
// Shortened timeout for on cycle
TCNT2 = 0x102;
}
else {
// LED is ON, turn it off
PORTB = 0x00;
}
}
int main(void)
{
// Disable digital input buffer on ADC pins
DIDR0 = (1 << ADC5D) | (1 << ADC4D) | (1 << ADC3D)
| (1 << ADC2D) | (1 << ADC1D) | (1 << ADC0D);
// Disable digital input buffer on Analog comparator pins
DIDR1 |= (1 << AIN1D) | (1 << AIN0D);
// Disable Analog Comparator interrupt
ACSR &= ~(1 << ACIE);
// Disable Analog Comparator
ACSR |= (1 << ACD);
// Disable unused peripherals to save power
// Disable ADC (ADC must be disabled before shutdown)
ADCSRA &= ~(1 << ADEN);
// Shut down the ADC
power_adc_disable();
// Disable SPI
power_spi_disable();
// Disable TWI
power_twi_disable();
// Disable the USART 0 module
power_usart0_disable();
// Disable the Timer 1 module
power_timer1_disable();
// Disable the Timer 0 module
power_timer0_disable();
// Change the clock prescaler
CLKPR = (1 << CLKPCE);
// Scale by DIV64
CLKPR = (1 << CLKPS2) | (1 << CLKPS1) | (0 << CLKPS0);
// Port B5 to output
DDRB = (1 << 5);
// Timer2 DIV 1024
TCCR2B = (1 << CS22) | (1 << CS21) | (1 << CS20);
// Overflow interrupt enable
TIMSK2 = (1 << TOIE2);
// Interrupts on
sei();
while (1) {
set_sleep_mode(SLEEP_MODE_PWR_SAVE);
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2020 Microchip Technology Inc.
User Guide
Power Debugger
Detailed Use Cases
DS40002201A-page 20