Rainbow-electronics ATmega8HVD Manuel d'utilisateur télécharger pdf (Page 32)

8052B–AVR–09/08

ATmega4HVD/8HVD

9. 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.

9.1 Sleep Modes

Figure 8-1 on page 22 presents the different clock systems in the ATmega4HVD/8HVD, and

their distribution. The figure is helpful in selecting an appropriate sleep mode. The different

sleep modes and their wake-up sources are summarized in Table 9-1, and Figure 9-1 on page

33 shows a sleep mode state diagram.

Note: 1. Discharge FET must be switched off for Charger Detect to be active.

To enter any of the available sleep modes, the SE bit in SMCR 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 (Idle, ADC NRM, Power-save or Power-off) will be activated by the SLEEP

instruction. See Table 9-3 on page 36 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. If a reset occurs during

sleep mode, the MCU wakes up and executes from the Reset Vector.

Table 9-1. Wake-up Sources for Sleep Modes

Mode

Wake-up sources

Battery Protection

Interrupts

External Interrupts

WDT

EEPROM Ready

VREGMON

ADC

Other I/O

Charger Detect

(1)

Idle

X XXXXXX

ADC Noise Reduction

X XXXXX

Power-save

XXX

Power-off

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Rainbow-electronics ATmega8HVD Manuel d'utilisateur Page 32