Rainbow Electronics ATmega128RFA1 - Manual (Page 158)

158
8266A-MCU Wireless-12/09
ATmega128RFA1
an external level interrupt on INT7:4 or a pin change interrupt can wakeup the MCU
from ADC Noise Reduction mode.
12.2.3 Power-down Mode
When the SM2:0 bits are written to 010, the SLEEP instruction makes the MCU enter
Power-down mode. In this mode, the 16 MHz crystal oscillator is stopped (if selected by
CKSEL fuses), while the external interrupts, the 2-wire Serial Interface, and the
Watchdog continue operating (if enabled). Only an External Reset, a Watchdog Reset,
a Brown-out Reset, 2-wire Serial Interface address match, an external level interrupt on
INT7:4, an external interrupt on INT3:0, a pin change interrupt, or a symbol counter
interrupt can wake up the MCU. This sleep mode basically halts all generated clocks,
allowing operation of asynchronous modules only.
Note that if a level triggered interrupt is used for wake-up from Power-down mode, the
changed level must be held for some time to wake up the MCU. Refer to section
"External Interrupts" on page 218 for details.
When waking up from Power-down mode, there is a delay from the wake-up condition
occurs until the wake-up becomes effective. This allows the clock to restart and become
stable after have been stopped. The wake-up period is defined by the same CKSEL
Fuses that define the Reset Time-out period, as described in chapter
"System Clock
and Clock Options" on page 147 .
12.2.4 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 enabled, it will keep running 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 TIMSK2, and the Global
Interrupt Enable bit in SREG is set. If Timer/Counter2 is not running, Power-down mode
is recommended instead of Power-save mode.
The Timer/Counter2 can be clocked both synchronously and asynchronously in Power-
save mode. If the Timer/Counter2 is not using the asynchronous clock, the
Timer/Counter Oscillator is stopped during sleep. If the Timer/Counter2 is not using the
synchronous clock, the clock source is stopped during sleep. Note that even if the
synchronous clock is running in Power-save, this clock is only available for the
Timer/Counter2. Timer/Counter2 operation is described in detail in section
"8-bit
Timer/Counter2 with PWM and Asynchronous Operation" on page 309 .
12.2.5 Standby Mode
When the SM2:0 bits are 110 and the crystal oscillator of the radio transceiver 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.
12.2.6 Extended Standby Mode
When the SM2:0 bits are 111 and the crystal oscillator of the radio transceiver 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.