ATtiny25 datasheet(127/196 Pages) ATMEL

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127

7598H–AVR–07/09

ATtiny25/45/85

• Bit 5 – IPR: Input Polarity Mode

The Input Polarity mode allows software selectable differential input pairs and full 10 bit ADC

resolution, in the unipolar input mode, assuming a pre-determined input polarity. If the input

polarity is not known it is actually possible to determine the polarity first by using the bipolar input

mode (with 9 bit resolution + 1 sign bit ADC measurement). And once determined, set or clear

the polarity reversal bit, as needed, for a succeeding 10 bit unipolar measurement.

• Bits 4..3 – Res: Reserved Bits

These bits are reserved bits in the ATtiny25/45/85 and will always read as zero.

• Bits 2:0 – ADTS2:0: ADC Auto Trigger Source

If ADATE in ADCSRA is written to one, the value of these bits selects which source will trigger

an ADC conversion. If ADATE is cleared, the ADTS2:0 settings will have no effect. A conversion

will be triggered by the rising edge of the selected Interrupt Flag. Note that switching from a trig-

ger source that is cleared to a trigger source that is set, will generate a positive edge on the

trigger signal. If ADEN in ADCSRA is set, this will start a conversion. Switching to Free Running

mode (ADTS[2:0]=0) will not cause a trigger event, even if the ADC Interrupt Flag is set.

18.7.9

Digital Input Disable Register 0 – DIDR0

• Bits 5..2 – ADC3D..ADC0D: ADC3..0 Digital Input Disable

When this bit is written logic one, the digital input buffer on the corresponding ADC pin is dis-

abled. The corresponding PIN register bit will always read as zero when this bit is set. When an

analog signal is applied to the ADC3..0 pin and the digital input from this pin is not needed, this

bit should be written logic one to reduce power consumption in the digital input buffer.

Table 18-6.

ADC Auto Trigger Source Selections

ADTS2

ADTS1

ADTS0

Trigger Source

Free Running mode

Analog Comparator

External Interrupt Request 0

Timer/Counter Compare Match A

Timer/Counter Overflow

Timer/Counter Compare Match B

Pin Change Interrupt Request

Bit

765

432

–

ADC0D

ADC2D

ADC3D

ADC1D

AIN1D

AIN0D

DIDR0

Read/Write

R/W

Initial Value

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