ATMEGA169P Datasheet, PDF (44/390 Pages) ATMEL Corporation – Microcontroller with 16K Bytes In-System Programmable Flash

8.9 Register Description
8.9.1 SMCR – Sleep Mode Control Register
The Sleep Mode Control Register contains control bits for power management.
Bit
7
6
5
4
3
2
1
0
0x33 (0x53)
–
–
–
–
SM2
SM1
SM0
SE
Read/Write
R
R
R
R
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
SMCR
• Bits 3, 2, 1 – SM2:0: Sleep Mode Select Bits 2, 1, and 0
These bits select between the five available sleep modes as shown in Table 8-2.
Table 8-2.
SM2
0
0
0
0
1
1
1
1
Sleep Mode Select
SM1
SM0
0
0
0
1
1
0
1
1
0
0
0
1
1
0
1
1
Sleep Mode
Idle
ADC Noise Reduction
Power-down
Power-save
Reserved
Reserved
Standby⁽¹⁾
Reserved
Note: 1. Standby mode is only recommended for use with external crystals or resonators.
8.9.2
• Bit 1 – SE: Sleep Enable
The SE bit must be written to logic one to make the MCU enter the sleep mode when the SLEEP
instruction is executed. To avoid the MCU entering the sleep mode unless it is the programmer’s
purpose, it is recommended to write the Sleep Enable (SE) bit to one just before the execution of
the SLEEP instruction and to clear it immediately after waking up.
PRR – Power Reduction Register
Bit
(0x64)
Read/Write
Initial Value
7
6
5
4
3
2
1
0
–
–
–
PRLCD PRTIM1 PRSPI PRUSART0 PRADC
PRR
R
R
R
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
• Bit 7:5 - Res: Reserved bits
These bits are reserved and will always read as zero.
• Bit 4 - PRLCD: Power Reduction LCD
Writing logic one to this bit shuts down the LCD controller. The LCD controller must be disabled
and the display discharged before shut down. See "Disabling the LCD" on page 217 for details
on how to disable the LCD controller.
44 ATmega169P
8018A–AVR–03/06