NAME

       avr_power - <avr/power.h>: Power Reduction Management

SYNOPSIS

   Functions
       void clock_prescale_set (clock_div_t __x)

Detailed Description

       #include <avr/power.h>

       Many AVRs contain a Power Reduction Register (PRR) or Registers (PRRx) that allow you to
       reduce power consumption by disabling or enabling various on-board peripherals as needed.
       Some devices have the XTAL Divide Control Register (XDIV) which offer similar
       functionality as System Clock Prescale Register (CLKPR).

       There are many macros in this header file that provide an easy interface to enable or
       disable on-board peripherals to reduce power. See the table below.

       Note
           Not all AVR devices have a Power Reduction Register (for example the ATmega8). On
           those devices without a Power Reduction Register, the power reduction macros are not
           available..

           Not all AVR devices contain the same peripherals (for example, the LCD interface), or
           they will be named differently (for example, USART and USART0). Please consult your
           device's datasheet, or the header file, to find out which macros are applicable to
           your device.

           For device using the XTAL Divide Control Register (XDIV), when prescaler is used,
           Timer/Counter0 can only be used in asynchronous mode. Keep in mind that Timer/Counter0
           source shall be less than ¼th of peripheral clock. Therefore, when using a typical
           32.768 kHz crystal, one shall not scale the clock below 131.072 kHz.

         Power Macro Description

       power_aca_disable() Disable the Analog Comparator on PortA.

       power_aca_enable() Enable the Analog Comparator on PortA.

       power_adc_enable() Enable the Analog to Digital Converter module.

       power_adc_disable() Disable the Analog to Digital Converter module.

       power_adca_disable() Disable the Analog to Digital Converter module on PortA

       power_adca_enable() Enable the Analog to Digital Converter module on PortA

       power_evsys_disable() Disable the EVSYS module

       power_evsys_enable() Enable the EVSYS module

       power_hiresc_disable() Disable the HIRES module on PortC

       power_hiresc_enable() Enable the HIRES module on PortC

       power_lcd_enable() Enable the LCD module.

       power_lcd_disable(). Disable the LCD module.

       power_pga_enable() Enable the Programmable Gain Amplifier module.

       power_pga_disable() Disable the Programmable Gain Amplifier module.

       power_pscr_enable() Enable the Reduced Power Stage Controller module.

       power_pscr_disable() Disable the Reduced Power Stage Controller module.

       power_psc0_enable() Enable the Power Stage Controller 0 module.

       power_psc0_disable() Disable the Power Stage Controller 0 module.

       power_psc1_enable() Enable the Power Stage Controller 1 module.

       power_psc1_disable() Disable the Power Stage Controller 1 module.

       power_psc2_enable() Enable the Power Stage Controller 2 module.

       power_psc2_disable() Disable the Power Stage Controller 2 module.

       power_ram0_enable() Enable the SRAM block 0 .

       power_ram0_disable() Disable the SRAM block 0.

       power_ram1_enable() Enable the SRAM block 1 .

       power_ram1_disable() Disable the SRAM block 1.

       power_ram2_enable() Enable the SRAM block 2 .

       power_ram2_disable() Disable the SRAM block 2.

       power_ram3_enable() Enable the SRAM block 3 .

       power_ram3_disable() Disable the SRAM block 3.

       power_rtc_disable() Disable the RTC module

       power_rtc_enable() Enable the RTC module

       power_spi_enable() Enable the Serial Peripheral Interface module.

       power_spi_disable() Disable the Serial Peripheral Interface module.

       power_spic_disable() Disable the SPI module on PortC

       power_spic_enable() Enable the SPI module on PortC

       power_spid_disable() Disable the SPI module on PortD

       power_spid_enable() Enable the SPI module on PortD

       power_tc0c_disable() Disable the TC0 module on PortC

       power_tc0c_enable() Enable the TC0 module on PortC

       power_tc0d_disable() Disable the TC0 module on PortD

       power_tc0d_enable() Enable the TC0 module on PortD

       power_tc0e_disable() Disable the TC0 module on PortE

       power_tc0e_enable() Enable the TC0 module on PortE

       power_tc0f_disable() Disable the TC0 module on PortF

       power_tc0f_enable() Enable the TC0 module on PortF

       power_tc1c_disable() Disable the TC1 module on PortC

       power_tc1c_enable() Enable the TC1 module on PortC

       power_twic_disable() Disable the Two Wire Interface module on PortC

       power_twic_enable() Enable the Two Wire Interface module on PortC

       power_twie_disable() Disable the Two Wire Interface module on PortE

       power_twie_enable() Enable the Two Wire Interface module on PortE

       power_timer0_enable() Enable the Timer 0 module.

       power_timer0_disable() Disable the Timer 0 module.

       power_timer1_enable() Enable the Timer 1 module.

       power_timer1_disable() Disable the Timer 1 module.

       power_timer2_enable() Enable the Timer 2 module.

       power_timer2_disable() Disable the Timer 2 module.

       power_timer3_enable() Enable the Timer 3 module.

       power_timer3_disable() Disable the Timer 3 module.

       power_timer4_enable() Enable the Timer 4 module.

       power_timer4_disable() Disable the Timer 4 module.

       power_timer5_enable() Enable the Timer 5 module.

       power_timer5_disable() Disable the Timer 5 module.

       power_twi_enable() Enable the Two Wire Interface module.

       power_twi_disable() Disable the Two Wire Interface module.

       power_usart_enable() Enable the USART module.

       power_usart_disable() Disable the USART module.

       power_usart0_enable() Enable the USART 0 module.

       power_usart0_disable() Disable the USART 0 module.

       power_usart1_enable() Enable the USART 1 module.

       power_usart1_disable() Disable the USART 1 module.

       power_usart2_enable() Enable the USART 2 module.

       power_usart2_disable() Disable the USART 2 module.

       power_usart3_enable() Enable the USART 3 module.

       power_usart3_disable() Disable the USART 3 module.

       power_usartc0_disable() Disable the USART0 module on PortC

       power_usartc0_enable() Enable the USART0 module on PortC

       power_usartd0_disable() Disable the USART0 module on PortD

       power_usartd0_enable() Enable the USART0 module on PortD

       power_usarte0_disable() Disable the USART0 module on PortE

       power_usarte0_enable() Enable the USART0 module on PortE

       power_usartf0_disable() Disable the USART0 module on PortF

       power_usartf0_enable() Enable the USART0 module on PortF

       power_usb_enable() Enable the USB module.

       power_usb_disable() Disable the USB module.

       power_usi_enable() Enable the Universal Serial Interface module.

       power_usi_disable() Disable the Universal Serial Interface module.

       power_vadc_enable() Enable the Voltage ADC module.

       power_vadc_disable() Disable the Voltage ADC module.

       power_all_enable() Enable all modules.

       power_all_disable() Disable all modules.

       Some of the newer AVRs contain a System Clock Prescale Register (CLKPR) that allows you to
       decrease the system clock frequency and the power consumption when the need for processing
       power is low. On some earlier AVRs (ATmega103, ATmega64, ATmega128), similar functionality
       can be achieved through the XTAL Divide Control Register. Below are two macros and an
       enumerated type that can be used to interface to the Clock Prescale Register or XTAL
       Divide Control Register.

       Note
           Not all AVR devices have a clock prescaler. On those devices without a Clock Prescale
           Register or XTAL Divide Control Register, these macros are not available.

       typedef enum
       {
           clock_div_1 = 0,
           clock_div_2 = 1,
           clock_div_4 = 2,
           clock_div_8 = 3,
           clock_div_16 = 4,
           clock_div_32 = 5,
           clock_div_64 = 6,
           clock_div_128 = 7,
           clock_div_256 = 8,
           clock_div_1_rc = 15, // ATmega128RFA1 only
       } clock_div_t;

        Clock prescaler setting enumerations for device using System Clock Prescale Register.

       typedef enum
       {
           clock_div_1 = 1,
           clock_div_2 = 2,
           clock_div_4 = 4,
           clock_div_8 = 8,
           clock_div_16 = 16,
           clock_div_32 = 32,
           clock_div_64 = 64,
           clock_div_128 = 128
       } clock_div_t;

        Clock prescaler setting enumerations for device using XTAL Divide Control Register.

Function Documentation

   clock_prescale_set (clock_div_t x)
       Set the clock prescaler register select bits, selecting a system clock division setting.
       This function is inlined, even if compiler optimizations are disabled.

       The type of x is clock_div_t.

       Note
           For device with XTAL Divide Control Register (XDIV), x can actually range from 1 to
           129. Thus, one does not need to use clock_div_t type as argument.

Author

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