Rainbow-electronics ATmega8515L Bedienungsanleitung PDF herunterladen (Seite 39)

ATmega8515(L)

2512A–AVR–04/02

• Bits 7 – SM0: Sleep Mode Select Bit 0

The SleepMode Select bitsselect between thethree available sleep modes asshown

in Table16.

Note: 1. Standby modeis only available with externalcrystals orresonators.

Idle Mode When the SM2..0 bits are writtento000, the SLEEPinstruction makes the MCU enter

Idlemode,stopping the CPUbut allowing SPI, USART, Analog Comparator,

Timer/Counters, Watchdog, and the Interrupt System to continue operating. Thissleep

mode basically haltsclk

CPU

andclk

FLASH

,whileallowing theotherclocks to run.

Idlemode enables the MCU to wakeupfrom external triggered interrupts aswell as

internal onesliketheTimerOverflow andUSART Transmit Complete interrupts. If

wake-upfrom theAnalog Comparator interruptis not required, theAnalog Comparator

can be powereddown by setting theACD bit in theAnalog ComparatorControl andSta-

tus Register –ACSR. Thiswill reduce powerconsumption in Idlemode.

Power-down Mode When the SM2..0 bits are writtento010, the SLEEPinstruction makes the MCU enter

Power-downmode. Inthis mode, theexternalOscillator isstopped, whilethe External

Interrupts and the Watchdog continue operating (if enabled). Only an External Reset, a

Watchdog Reset, a Brown-out Reset, an Externallevel interruptonINT0 orINT1, or an

External interruptonINT2 can wakeup the MCU.Thissleep mode basically halts all

generatedclocks, allowing operation of asynchronous modules only.

Note that if a level triggered interruptis usedforwake-upfrom Power-downmode, the

changedlevel must be held forsometimetowakeup the MCU.Refer to “ExternalInter-

rupts”onpage 74 fordetails.

When waking upfrom Power-downmode, thereis a delayfrom the wake-upcondition

occurs until the wake-upbecomes effective. This allows the clock to restartandbecome

stableafterhaving been stopped.The wake-upperiod isdefinedbythe same CKSEL

Fuses that define theReset Time-out period, asdescribed in “Clock Sources”onpage

32.

Table 16. SleepMode Select

SM2 SM1 SM0 Sleep Mode

000Idle

001Reserved

010Power-down

011Reserved

100Reserved

101Reserved

110Standby

(1)

111Reserved

1 2 ... 34 35 36 37 38 39 40 41 42 43 44 ... 222 223

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