atmega32u4-16mu ATMEL Corporation, atmega32u4-16mu Datasheet - Page 43

• Manufacturer Part Number: atmega32u4-16mu
• Description: Atmega32u4 8-bit Avr Microcontroller With 32k Bytes Of Isp Flash And Usb Controller
• Manufacturer: ATMEL Corporation

7.5
7.6
Table 7-2.
Notes:
7.7
7.7.1
7766A–AVR–03/08
Sleep Mode
Idle
ADCNRM
Power-down
Power-save
Standby
Extended
Standby
Standby Mode
Extended Standby Mode
1. Only recommended with external crystal or resonator selected as clock source.
2. For INT6, only level interrupt.
3. Asynchronous USB interrupts are VBUSTI and WAKEUPI.
Power Reduction Register
(1)
Power Reduction Register 0 - PRR0
Active Clock Domains and Wake-up Sources in the Different Sleep Modes.
Active Clock Domains
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.
When the SM2..0 bits are 111 and an external crystal/resonator clock option is selected, the
SLEEP instruction makes the MCU enter Extended Standby mode. For compatibility reasons
with AT90USB64/128 this mode is still present but since Timer 2 Asynchronous operation is not
present here, this mode is identical to Standby-mode.
The Power Reduction Register, PRR, provides a method to stop the clock to individual peripher-
als to reduce power consumption. The current state of the peripheral is frozen and 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.
Bit
Read/Write
X
X
X
7
PRTWI
R/W
Oscillators
6
PRTIM2
R/W
X
X
X
X
“Supply Current of IO modules” on page 429
5
PRTIM0
R/W
X
X
X
X
X
X
(2)
(2)
(2)
(2)
(2)
4
–
R
X
X
X
X
X
X
3
PRTIM1
R/W
X
X
Wake-up Sources
X
X
2
PRSPI
R/W
X
X
X
X
X
X
1
-
R
X
ATmega32U4
for examples. In all other
X
X
0
PRADC
R/W
X
X
X
X
X
X
PRR0
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