40
ATmega8515(L)
2512A–AVR–04/02
Standby Mode When the SM2..0 bits are written to 110, and an externalcrystal/resonatorclock option
isselected, the SLEEPinstruction makes the MCU enterStandby mode. This modeis
identical to Power-down with theexception that the Oscillator iskept running. From
Standby mode, the device wakes up in sixclock cycles.
Notes: 1. ExternalCrystal orresonatorselected asclock source
2. Only INT2 orlevel interrupt INT1 andINT0
Minimizing Power
Consumption
Thereare several issues to considerwhen trying to minimizethe powerconsumption in
an AVR controlled system. In general, sleep modesshould beused as much aspossi-
ble, and the sleep mode should be selectedsothat asfew aspossibleof the device’s
functions areoperating. All functions not neededshould be disabled. In particular, the
following modules may needspecialconsideration when tryingtoachieve the lowest
possible powerconsumption.
Analog Comparator When entering Idlemode, theAnalog Comparatorshould be disabled if not needed. In
theothersleep modes, theAnalog Comparator is automatically disabled. However, if
theAnalog Comparator isset up to usethe Internal Voltage Referenceas input, the
Analog Comparatorshould be disabled in all sleep modes. Otherwise, the Internal Volt-
age Reference will beenabled, independent ofsleep mode. Refer to “Analog
Comparator”onpage 160 fordetails on how to configuretheAnalog Comparator.
Brown-out Detector If the Brown-out Detector is not needed in theapplication, this module should beturned
off. If the Brown-out Detector is enabledbythe BODEN Fuse, it will beenabled in all
sleep modes, andhence, always consume power. Inthe deepersleep modes, thiswill
contribute significantly to thetotalcurrent consumption. Refer to “Brown-out Detection”
on page 45 fordetails on how to configurethe Brown-out Detector.
Internal Voltage Reference The Internal Voltage Reference will be enabledwhen neededbythe Brown-out Detector
or theAnalog Comparator. If thesemodules are disabled asdescribed in the sections
above, theinternal voltage reference will be disabled and it will not be consuming
power. When turned on again, theuser mustallow the referencetostartupbeforethe
output is used. If the referenceiskeptoninsleep mode, the output can beused imme-
diately.Refer to “Internal Voltage Reference” on page 47fordetails on the start-up time.
Watchdog Timer If the Watchdog Timer is not needed in theapplication, this module should beturned off.
If the Watchdog Timer is enabled, it will be enabled in all sleep modes, andhence,
always consume power. Inthe deepersleep modes, thiswill contribute significantly to
thetotalcurrent consumption. Refer to page 50 fordetails on how to configurethe
Watchdog Timer.
Table 17. Active Clock Domains andWake-upSources in the Different SleepModes
Active Clock domains Oscillators Wake-up Sources
Sleep Mode clk
CPU
clk
FLASH
clk
IO
Main Clock
Source Enabled
INT2
INT1
INT0
SPM/
EEPROM
Ready OtherI/O
Idle
XX XXX
Power-down X
(2)
Standby
(1)
XX
(2)
(151 paginas)
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