ATA8741 ATMEL Corporation, ATA8741 Datasheet - Page 51

• Manufacturer Part Number: ATA8741
• Manufacturer: ATMEL Corporation

15.3
15.4
15.5
15.6
9140B–INDCO–07/09
ADC Noise Reduction Mode
Power-down Mode
Power Reduction Register
Standby Mode
the Analog Comparator can be powered down by setting the ACD bit in the Analog Comparator
Control and Status Register – ACSR. This will reduce power consumption in Idle mode. If the
ADC is enabled, a conversion starts automatically when this mode is entered.
When the SM1..0 bits are written to 01, the SLEEP instruction makes the MCU enter ADC Noise
Reduction mode, stopping the CPU but allowing the ADC, the external interrupts, and the
Watchdog to continue operating (if enabled). This sleep mode halts clk
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 form the
ADC Conversion Complete interrupt, only an External Reset, a Watchdog Reset, a Brown-out
Reset, an SPM/EEPROM ready interrupt, an external level interrupt on INT0 or a pin change
interrupt can wake up the MCU from ADC Noise Reduction mode.
When the SM1..0 bits are written to 10, the SLEEP instruction makes the MCU enter
Power-down mode. In this mode, the 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, an external level interrupt on INT0, or a pin change interrupt can wake up the
MCU. This sleep mode 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. See
details
When the SM1..0 bits are 11 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.
The Power Reduction Register (PRR), see
vides a method to stop the clock to individualperipherals to reduce power consumption. The
current state of the peripheral is frozenand the I/O registers can not be read or written.
Resources used by the peripheral when stopping the clock will remain occupied, hence the
peripheral should in most cases be disabled before stopping the clock. Waking up a module,
which is done by clearing the bit in PRR, puts the module in the same state as before shutdown.
Module shutdown can be used in Idle mode and Active mode to significantly reduce the overall
power consumption. See
sleep modes, the clock is already stopped.
“Power-down Supply Current” on page 212
“PRR – Power Reduction Register” on page
“External Interrupts” on page 68
for examples. In all other
I/O
, clk
CPU
ATA8741
, and clk
54, pro-
FLASH
for
51
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