AT90USB1286-16MU ATMEL [ATMEL Corporation], AT90USB1286-16MU Datasheet - Page 56

• Manufacturer Part Number: AT90USB1286-16MU
• Description: Microcontroller with 64/128K Bytes of ISP Flash and USB Controller
• Manufacturer: ATMEL [ATMEL Corporation]

7.7.2
7.8
7.8.1
7.8.2
56
Minimizing Power Consumption
AT90USB64/128
Power Reduction Register 1 - PRR1
Analog to Digital Converter
Analog Comparator
• 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..4 - Res: Reserved bits
These bits are reserved and will always read as zero.
• Bit 3 - PRTIM3: Power Reduction Timer/Counter3
Writing a logic one to this bit shuts down the Timer/Counter3 module. When the Timer/Counter3
is enabled, operation will continue like before the shutdown.
• Bit 2..1 - Res: Reserved bits
These bits are reserved and will always read as zero.
• Bit 0 - PRUSART1: Power Reduction USART1
Writing a logic one to this bit shuts down the USART1 by stopping the clock to the module.
When waking up the USART1 again, the USART1 should be re initialized to ensure proper
operation.
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.
If enabled, the ADC will be enabled in all sleep modes. To save power, the ADC should be dis-
abled before entering any sleep mode. When the ADC is turned off and on again, the next
conversion will be an extended conversion. Refer to
316
When entering Idle mode, the Analog Comparator should be disabled if not used. When entering
ADC Noise Reduction mode, the Analog Comparator should be disabled. 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 disabled in all
sleep modes. Otherwise, the Internal Voltage Reference will be enabled, independent of sleep
mode. Refer to
Comparator.
Bit
Read/Write
Initial Value
for details on ADC operation.
7
PRUSB
R/W
0
“Analog Comparator” on page 313
6
–
R
0
5
–
R
0
4
–
R
0
3
PRTIM3
R/W
0
“Analog to Digital Converter - ADC” on page
for details on how to configure the Analog
2
–
R
0
1
–
R
0
0
PRUSART1
R/W
0
PRR1
7593A–AVR–02/06