31
2543L–AVR–08/10
ATtiny2313
Power-down Mode When the SM1..0 bits are written to 01 or 11, the SLEEP instruction makes the MCU enter
Power-down mode. In this mode, the external Oscillator is stopped, while the external interrupts,
the USI start condition detection, and the Watchdog continue operating (if enabled). Only an
External Reset, a Watchdog Reset, a Brown-out Reset, USI start condition interrupt, an external
level interrupt on INT0, or a pin change interrupt can wake up the MCU. This sleep mode basi-
cally 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
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
having been stopped. The wake-up period is defined by the same CKSEL Fuses that define the
Standby Mode
When the SM1..0 bits are 10 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.
Notes: 1. Only recommended with external crystal or resonator selected as clock source.
2. For INT0, only level interrupt.
Minimizing Power
Consumption
There are several issues to consider when trying to minimize the power consumption in an AVR
controlled system. In general, sleep modes should be used as much as possible, and the sleep
mode should be selected so that as few as possible of the device’s functions are operating. All
functions not needed should be disabled. In particular, the following modules may need special
consideration when trying to achieve the lowest possible power consumption.
Analog Comparator
When entering Idle mode, the Analog Comparator should be disabled if not used. In other sleep
modes, the Analog Comparator is automatically disabled. However, if the Analog Comparator is
set up to use the Internal Voltage Reference as input, the Analog Comparator should be dis-
abled in all sleep modes. Otherwise, the Internal Voltage Reference will be enabled,
configure the Analog Comparator.
Brown-out Detector
If the Brown-out Detector is not needed by the application, this module should be turned off. If
the Brown-out Detector is enabled by the BODLEVEL Fuses, it will be enabled in all sleep
modes, and hence, always consume power. In the deeper sleep modes, this will contribute sig-
Table 14. Active Clock Domains and Wake-up Sources in the Different Sleep Modes.
Active Clock Domains Oscillators
Wake-up Sources
Sleep Mode
clk
CP
U
clk
FLA
SH
clk
IO
En
ab
le
d
IN
T0,
INT1
and
Pi
n
Ch
an
ge
USI
S
tar
t
Condition
S
P
M/EEPROM
Read
y
Oth
er
I/
O
WDT
Idle
X
XXXX
X
Power-down
XX
XX