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 clkASY, allowing operation only of asyn-
chronous modules, including Timer/Counter2 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 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 Oscillator is kept running.
From Extended Standby mode, the device wakes up in six clock cycles..
Table 14. Active Clock Domains and Wake Up Sources in the Different Sleep Modes
Active Clock domains
Oscillators
Wake-up Sources
SPM /
INT2
INT1
INT0
TWI
Address
Match
Sleep
Mode
Main Clock
clkCPU clkFLASH clkIO clkADC clkASY Source Enabled
Timer Osc.
Enabled
Timer
2
EEPROM
Ready
Other
I/O
ADC
Idle
X
X
X
X
X(2)
X
X
X
X
X
X
ADC
Noise
Redu-
ction
X
X
X
X(2)
X(3)
X
X
X
X
Power
Down
X(3)
X
Power
Save
X(2)
X(2)
X(3)
X(3)
X
X
X(2)
Standby(1)
X
X
Exten-
ded
X(2)
X(2)
X(3)
X
X(2)
Standby(1)
Notes: 1. External Crystal or resonator selected as clock source.
2. If AS2 bit in ASSR is set.
3. Only INT2 or level interrupt INT1 and INT0.
32
ATmega16(L)
2466E–AVR–10/02
ATMEL [ ATMEL ]
