Datasheet

Table Of Contents
13.9.1. MCUCR – MCU Control Register
The MCU Control Register contains control bits for power management.
When using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be used. When
addressing I/O Registers as data space using LD and ST instructions, 0x20 must be added to these offset
addresses.
Name:  MCUCR
Offset:  0x35
Reset:  0x00
Property:
 
When addressing I/O Registers as data space the offset address is 0x55
Bit 7 6 5 4 3 2 1 0
SE SM2 SM1 SM0
Access
R/W R/W R/W R/W
Reset 0 0 0 0
Bit 7 – 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 set the Sleep Enable (SE) bit to one just before the execution of the SLEEP
instruction and to clear it immediately after waking up.
Bits 6:4 – SMn: Sleep Mode n Select Bits [n = 2:0]
These bits select between the six available sleep modes as shown in the table.
Table 13-2. Sleep Mode Select
SM2 SM1 SM0 Sleep Mode
0 0 0 Idle
0 0 1 ADC Noise Reduction
0 1 0 Power-down
0 1 1 Power-save
1 0 0 Reserved
1 0 1 Reserved
1 1 0 Standby
(1)
1 1 1 Extended Standby
(1)
Note:  1. Standby mode is only available with external crystals or resonators.
Atmel ATmega32A [DATASHEET]
Atmel-8155I-ATmega32A_Datasheet_Complete-08/2016
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