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2513L–AVR–03/2013
ATmega162/V
Power-save Mode
When the SM2..0 bits are written to 011, the SLEEP instruction makes the MCU enter Power-
save mode. This mode is identical to Power-down, with one exception:
If Timer/Counter2 is clocked asynchronously, i.e., the AS2 bit in ASSR is set, Timer/Counter2
will run during sleep. The device can wake up from either Timer Overflow or Output Compare
event from Timer/Counter2 if the corresponding Timer/Counter2 interrupt enable bits are set in
TIMSK, and the Global Interrupt Enable bit in SREG is set.
If the Asynchronous Timer is NOT clocked asynchronously, Power-down mode is recommended
instead of Power-save mode because the contents of the registers in the Asynchronous Timer
should be considered undefined after wake-up in Power-save mode if AS2 is 0.
This sleep mode basically halts all clocks except clk
ASY, allowing operation only of asynchronous
modules, including Timer/Counter 2 if clocked asynchronously.
Standby Mode
When the SM2..0 bits are 110 and an external crystal/resonator clock option is selected, the
SLEEP instruction makes the MCU enter Standby mode. This mode is identical to Power-down
with the exception that the main Oscillator is kept running. From Standby mode, the device
wakes up in six clock cycles.
Extended Standby
Mode
When the SM2..0 bits are 111 and an external crystal/resonator clock option is selected, the
SLEEP instruction makes the MCU enter Extended Standby mode. This mode is identical to
Power-save mode with the exception that the main Oscillator is kept running. From Extended
Standby mode, the device wakes up in six clock cycles.
Notes:
1. External Crystal or resonator selected as clock source
2. If AS
2 bit in ASSR is set
3. For INT1 and INT0, only level interrupt
Table 17. Active Clock domains and Wake up sources in the different sleep modes
Active Clock domains
Oscillators
Wake-up Sources
Sleep Mode
clk
CPU
clk
FLASH
clk
IO
clk
ASY
Main Clock
Source Enabled
Timer Osc
Enabled
INT2
INT1
INT0
and Pin Change
Timer
2
SPM/
EEPROM
Ready
Other
I/O
Idle
X
XX
X
Power-down
Power-save