ATmega32A Datasheet - Sunrom Technologies

ATmega32AIf the Asynchronous Timer is NOT clocked asynchronously, Power-down mode is recommendedinstead of Power-save mode because the contents of the registers in the Asynchronous Timershould be considered undefined after wake-up in Power-save mode if AS2 is 0.This sleep mode basically halts all clocks except clk ASY , allowing operation only of asynchronousmodules, including Timer/Counter2 if clocked asynchronously.9.6 Standby ModeWhen the SM2:0 bits are 110 and an external crystal/resonator clock option is selected, theSLEEP instruction makes the MCU enter Standby mode. This mode is identical to Power-downwith the exception that the Oscillator is kept running. From Standby mode, the device wakes upin six clock cycles.9.7 Extended Standby ModeWhen the SM2:0 bits are 111 and an external crystal/resonator clock option is selected, theSLEEP instruction makes the MCU enter Extended Standby mode. This mode is identical toPower-save mode with the exception that the Oscillator is kept running. From Extended Standbymode, the device wakes up in six clock cycles.9.8 Minimizing Power ConsumptionThere are several issues to consider when trying to minimize the power consumption in an AVRcontrolled system. In general, sleep modes should be used as much as possible, and the sleepmode should be selected so that as few as possible of the device’s functions are operating. Allfunctions not needed should be disabled. In particular, the following modules may need specialconsideration when trying to achieve the lowest possible power consumption.9.8.1 Analog to Digital ConverterIf enabled, the ADC will be enabled in all sleep modes. To save power, the ADC should be disabledbefore entering any sleep mode. When the ADC is turned off and on again, the nextconversion will be an extended conversion. Refer to “Analog to Digital Converter” on page 209for details on ADC operation.9.8.2 Analog ComparatorWhen entering Idle mode, the Analog Comparator should be disabled if not used. When enteringADC Noise Reduction mode, the Analog Comparator should be disabled. In the other sleepmodes, the Analog Comparator is automatically disabled. However, if the Analog Comparator isset up to use the Internal Voltage Reference as input, the Analog Comparator should be disabledin all sleep modes. Otherwise, the Internal Voltage Reference will be enabled,independent of sleep mode. Refer to “Analog Comparator” on page 206 for details on how toconfigure the Analog Comparator.9.8.3 Brown-out DetectorIf the Brown-out Detector is not needed in the application, this module should be turned off. If theBrown-out Detector is enabled by the BODEN Fuse, it will be enabled in all sleep modes, andhence, always consume power. In the deeper sleep modes, this will contribute significantly tothe total current consumption. Refer to “Brown-out Detector” on page 35 for details on how toconfigure the Brown-out Detector.8155C–AVR–02/1135