ATmega16U4 datasheet(45/408 Pages) ATMEL

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7766D–AVR–01/09

ATmega16U4/ATmega32U4

• Bit 7 - PRTWI: Power Reduction TWI

Writing a logic one to this bit shuts down the TWI by stopping the clock to the module. When

waking up the TWI again, the TWI should be re initialized to ensure proper operation.

• Bit 6 - Res: Reserved bit

This bits is reserved and will always read as zero.

• Bit 5 - PRTIM0: Power Reduction Timer/Counter0

Writing a logic one to this bit shuts down the Timer/Counter0 module. When the Timer/Counter0

is enabled, operation will continue like before the shutdown.

• Bit 4 - Res: Reserved bit

This bit is reserved and will always read as zero.

• Bit 3 - PRTIM1: Power Reduction Timer/Counter1

Writing a logic one to this bit shuts down the Timer/Counter1 module. When the Timer/Counter1

is enabled, operation will continue like before the shutdown.

• Bit 2 - PRSPI: Power Reduction Serial Peripheral Interface

Writing a logic one to this bit shuts down the Serial Peripheral Interface by stopping the clock to

the module. When waking up the SPI again, the SPI should be re initialized to ensure proper

operation.

• Bit 1 - Res: Reserved bit

These bits are reserved and will always read as zero.

• Bit 0 - PRADC: Power Reduction ADC

Writing a logic one to this bit shuts down the ADC. The ADC must be disabled before shut down.

The analog comparator cannot use the ADC input MUX when the ADC is shut down.

7.7.2

Power Reduction Register 1 - PRR1

• Bit 7 - PRUSB: Power Reduction USB

Writing a logic one to this bit shuts down the USB by stopping the clock to the module. When

waking up the USB again, the USB should be re initialized to ensure proper operation.

• Bit 6..5 - Res: Reserved bits

These bits are reserved and will always read as zero.

• Bit 4- PRTIM4: Power Reduction Timer/Counter4

Writing a logic one to this bit shuts down the Timer/Counter4 module. When the Timer/Counter4

is enabled, operation will continue like before the shutdown.

• Bit 3 - PRTIM3: Power Reduction Timer/Counter3

Initial Value

0000

Bit

654

PRUSB

–

PRTIM4

PRTIM3

–

PRUSART1

PRR1

Read/Write

R/W

Initial Value

ATmega16U4 Datasheet(PDF) 45 Page - ATMEL Corporation

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