Datasheet

45
8018P–AVR–08/10
ATmega169P
9.9 Register Description
9.9.1 SMCR – Sleep Mode Control Register
The Sleep Mode Control Register contains control bits for power management.
• 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 9-2.
Note: 1. Standby mode is only recommended for use with external crystals or resonators.
• 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.
9.9.2 PRR – Power Reduction Register
• 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 244 for details
on how to disable the LCD controller.
Bit 76543210
0x33 (0x53)
– – – – SM2 SM1 SM0 SE SMCR
Read/Write R R R R R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Table 9-2. Sleep Mode Select
SM2 SM1 SM0 Sleep Mode
000Idle
0 0 1 ADC Noise Reduction
0 1 0 Power-down
0 1 1 Power-save
100Reserved
101Reserved
1 1 0 Standby
(1)
111Reserved
Bit 7 6 5 4 3 2 1 0
(0x64) – – – PRLCD PRTIM1 PRSPI PRUSART0 PRADC PRR
Read/Write R R R R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0