Datasheet

34
8024A–AVR–04/08
ATmega8HVA/16HVA
10. Power Management and Sleep Modes
Sleep modes enable the application to shut down unused modules in the MCU, thereby saving
power. The AVR provides various sleep modes allowing the user to tailor the power consump-
tion to the application’s requirements.
10.1 Sleep Modes
Figure 9-1 on page 24 presents the different clock systems in the ATmega8HVA/16HVA, and
their distribution. The figure is helpful in selecting an appropriate sleep mode. The different sleep
modes and their wake up sources is summarized in Table 10-1, and Figure 10-1 on page 35
shows a sleep mode state diagram.
Notes: 1. Discharge FET must be switched off for Charger Detect to be active.
2. Instantaneous and Accumulate Conversion Complete wake-up only.
To enter any of the sleep modes, the SE bit in SMCR, see ”SMCR – Sleep Mode Control Regis-
ter” on page 39, must be written to logic one and a SLEEP instruction must be executed. The
SM2..0 bits in the SMCR Register select which sleep mode will be activated by the SLEEP
instruction. See Table 10-3 on page 39 for a summary.
If an enabled interrupt occurs while the MCU is in a sleep mode, the MCU wakes up. The MCU
is then halted for four cycles in addition to the start-up time, executes the interrupt routine, and
resumes execution from the instruction following SLEEP. The contents of the register file and
SRAM are unaltered when the device wakes up from any sleep mode except Power-off. If a
reset occurs during sleep mode, the MCU wakes up and executes from the Reset Vector.
Table 10-1. Wake-up Sources for Sleep Modes
Mode
Wake-up sources
Wake-up on Regular Current Battery Protection Interrupts External Interrupts WDT EEPROM Ready VREGMON CC-ADC V-ADC Other I/O Charger Detect
(1)
Idle
X X XXXXX
(2)
XX
ADC Noise Reduction
X X XXXXX
(2)
X
Power-save
XXXX X
(2)
Power-off
X