Datasheet

23
ATtiny4/5/9/10 [DATASHEET]
8127F–AVR–02/2013
7. Power Management and Sleep Modes
The high performance and industry leading code efficiency makes the AVR microcontrollers an ideal choise for low
power applications. In addition, sleep modes enable the application to shut down unused modules in the MCU,
thereby saving power. The AVR provides various sleep modes allowing the user to tailor the power consumption to
the application’s requirements.
7.1 Sleep Modes
Figure 6-1 on page 17 presents the different clock systems and their distribution in ATtiny4/5/9/10. The figure is
helpful in selecting an appropriate sleep mode. Table 7-1 shows the different sleep modes and their wake up
sources.
Note: 1. The ADC is available in ATtiny5/10, only
2. For INT0, only level interrupt.
To enter any of the four sleep modes, the SE bits in SMCR must be written to logic one and a SLEEP instruction
must be executed. The SM2:0 bits in the SMCR register select which sleep mode (Idle, ADC Noise Reduction,
Standby or Power-down) will be activated by the SLEEP instruction. See Table 7-2 for a summary.
If an enabled interrupt occurs while the MCU is in a sleep mode, the MCU wakes up. The MCU is then halted for
four cycles in addition to the start-up time, executes the interrupt routine, and resumes execution from the instruc-
tion following SLEEP. The contents of the Register File and SRAM are unaltered when the device wakes up from
sleep. If a reset occurs during sleep mode, the MCU wakes up and executes from the Reset Vector.
Note that if a level triggered interrupt is used for wake-up the changed level must be held for some time to wake up
the MCU (and for the MCU to enter the interrupt service routine). See “External Interrupts” on page 36 for details.
7.1.1 Idle Mode
When bits SM2:0 are written to 000, the SLEEP instruction makes the MCU enter Idle mode, stopping the CPU but
allowing the analog comparator, timer/counter, watchdog, and the interrupt system to continue operating. This
sleep mode basically halts clk
CPU
and clk
NVM
, while allowing the other clocks to run.
Idle mode enables the MCU to wake up from external triggered interrupts as well as internal ones like the timer
overflow. If wake-up from the analog comparator interrupt is not required, the analog comparator can be powered
down by setting the ACD bit in “ACSR – Analog Comparator Control and Status Register” on page 80. This will
reduce power consumption in idle mode. If the ADC is enabled (ATtiny5/10, only), a conversion starts automatically
when this mode is entered.
Table 7-1. Active Clock Domains and Wake-up Sources in Different Sleep Modes
Sleep Mode
Active Clock Domains Oscillators Wake-up Sources
clk
CPU
clk
NVM
clk
IO
clk
ADC
(1)
Main Clock Source Enabled INT0 and Pin Change ADC
(1)
Other I/O Watchdog Interrupt VLM Interrupt
Idle XX X XXXXX
ADC Noise Reduction X X X
(2)
XXX
Standby X X
(2)
X
Power-down X
(2)
X