atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 41

• Manufacturer Part Number: atmega32c1
• Description: Atmega32m1 Automotive 8-bit Avr Microcontroller With 32k/64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

6.6
6.6.1
7647A–AVR–02/08
Power Reduction Register
Power Reduction Register - PRR
with the exception that the Oscillator is kept running. From Standby mode, the device wakes up
in six clock cycles.
Table 6-2.
Notes:
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.
A full predictible behaviour of a peripheral is not guaranteed during and after a cycle of stopping
and starting of its clock. So its recommended to stop a peripheral before stopping its clock with
PRR register.
Module shutdown can be used in Idle mode and Active mode to significantly reduce the overall
power consumption. In all other sleep modes, the clock is already stopped.
• Bit 7 - Res: Reserved Bit
This bit is unused bit in the ATmega32/64/M1/C1, and will always read as zero.
• Bit 6 - PRCAN: Power Reduction CAN
Writing a logic one to this bit reduces the consumption of the CAN by stopping the clock to this
module. When waking up the CAN again, the CAN should be re initialized to ensure proper
operation.
• Bit 5 - PRPSC: Power Reduction PSC
Bit
Read/Write
Initial Value
Sleep
Mode
Idle
ADC
Noise
Reduction
Power-
down
Standby
1. Only recommended with external crystal or resonator selected as clock source.
2. Only level interrupt.
(1)
Active Clock Domains and Wake-up Sources in the Different Sleep Modes.
R
7
0
-
Active Clock Domains
PRCAN
R/W
6
0
X
PRPSC
X
X
R/W
5
0
X
X
PRTIM1
R/W
4
0
Oscillator
X
X
X
s
PRTIM0
R/W
3
0
ATmega32/64/M1/C1
X
X
X
X
(2)
(2)
(2)
PRSPI
R/W
2
0
X
X
Wake-up Sources
PRLIN
R/W
1
0
X
X
PRADC
X
X
R/W
0
0
X
X
X
X
PRR
X
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