Rainbow Electronics ATtiny26L - Manual (Page 42)

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ATtiny26(L)
1477B–AVR–04/02
Note that if a level triggered external interrupt or pin change interrupt is used from
Power-down mode, the changed level must be held for some time to wake up the MCU.
This makes the MCU less sensitive to noise. The changed level is sampled twice by the
Watchdog Oscillator clock, and if both these samples have the required level, the MCU
will wake up. The period of the Watchdog Oscillator is 1.0
µs (nominal) at 3.0V and
25°C. The frequency of the Watchdog Oscillator is voltage dependent as shown in the
Electrical Characteristics section.
If the wake-up condition disappears before the MCU wakes up and starts to execute,
e.g., a low level on INT0 is not held long enough, the interrupt causing the wake-up will
not be executed.
Standby Mode When the SM1..0 bits are “11” and an External Crystal/Resonator clock option is
selected, the SLEEP instruction forces the MCU into the 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 only six clock cycles.
Notes: 1. Only recommended with external crystal or resonator selected as clock source.
2. Only level interrupt INT0.
Table 20. 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
ADC
Main Clock
Source Enabled
INT0, and Pin
Change
USI Start
Condition
EEPROM
Ready
ADC Other I/O
Idle X X X X X X X X
ADC Noise
Reduction
X X X (2) X X X
Power-down X (2) X
Standby (1) X X (2) X