36
AT90PWM216/316 [DATASHEET]
7710H–AVR–07/2013
Idle mode enables the MCU to wake up from external triggered interrupts as well as internal ones like the Timer
Overflow and USART Transmit Complete interrupts. If the ADC is enabled, a conversion starts automatically when
this mode is entered.
7.2
ADC Noise Reduction Mode
When the SM2..0 bits are written to 001, the SLEEP instruction makes the MCU enter ADC Noise Reduction mode,
stopping the CPU but allowing the ADC, the External Interrupts, Timer/Counter (if their clock source is external - T0
or T1) and the Watchdog to continue operating (if enabled). This sleep mode basically halts clk
I/O, clkCPU, and
clk
FLASH, while allowing the other clocks to run.
This improves the noise environment for the ADC, enabling higher resolution measurements. If the ADC is
enabled, a conversion starts automatically when this mode is entered. Apart from the ADC Conversion Complete
interrupt, only an External Reset, a Watchdog Reset, a Brown-out Reset, a Timer/Counter interrupt, an
SPM/EEPROM ready interrupt, an External Level Interrupt on INT3:0 can wake up the MCU from ADC Noise
Reduction mode.
7.3
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 External Oscillator is stopped, while the External Interrupts and the Watchdog continue operating (if
enabled). Only an External Reset, a Watchdog Reset, a Brown-out Reset, a PSC Interrupt, an External Level Inter-
rupt on INT3:0 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
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 Reset Time-out period, as described in
“Clock Sources”7.4
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.
Notes:
1. Only recommended with external crystal or resonator selected as clock source.
2. Only level interrupt.
Table 7-2.
Active Clock Domains and Wake-up Sources in the Different Sleep Modes.
Active Clock Domains
Oscillators
Wake-up Sources
Sleep Mode
clk
CP
U
cl
k
FLASH
clk
IO
clk
AD
C
clk
PLL
Ma
in
Clock
Source
Ena
b
led
INT3..
0
PSC
SPM/EEPROM
R
eady
ADC
WDT
OtherI/O
Idle
XXX
X
ADC Noise Reduction
X
XX
X
Power-down
XX
X