ATtiny43U datasheet(127/182 Pages) ATMEL

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8048B–AVR–03/09

• Bits 2:0 – MUX[2:0]: Analog Channel Selection Bits

The value of these bits selects which analog input is connected to the ADC, as shown in Table

16-4. Selecting channel ADC4 enables temperature measurement.

Notes:

1. Due to the voltage divider present, a current will flow from VBAT to ground via a 100kΩ resistor

divider as long as this channel is selected.

2. See “Temperature Measurement” on page 125.

If these bits are changed during a conversion, the change will not go into effect until this

conversion is complete (ADIF in ADCSRA is set).

16.13.2

ADCSRA – ADC Control and Status Register A

• Bit 7 – ADEN: ADC Enable

Writing this bit to one enables the ADC. By writing it to zero, the ADC is turned off. Turning the

ADC off while a conversion is in progress, will terminate this conversion.

• Bit 6 – ADSC: ADC Start Conversion

In Single Conversion mode, write this bit to one to start each conversion. In Free Running mode,

write this bit to one to start the first conversion. The first conversion after ADSC has been written

after the ADC has been enabled, or if ADSC is written at the same time as the ADC is enabled,

will take 25 ADC clock cycles instead of the normal 13. This first conversion performs initializa-

tion of the ADC.

ADSC will read as one as long as a conversion is in progress. When the conversion is complete,

it returns to zero. Writing zero to this bit has no effect.

• Bit 5 – ADATE: ADC Auto Trigger Enable

When this bit is written to one, Auto Triggering of the ADC is enabled. The ADC will start a con-

version on a positive edge of the selected trigger signal. The trigger source is selected by setting

the ADC Trigger Select bits, ADTS in ADCSRB.

Table 16-4.

ADC Multiplexer Channel Selections.

Single Ended Input

MUX[2:0]

ADC0 (PA0)

000

ADC1 (PA1)

001

ADC2 (PA2)

010

ADC3 (PA3)

011

0V (GND)

100

1.1V (I Ref)

101

BAT

(1)

110

ADC4 (2)

111

Bit

7654

321

0x06 (0x26)

ADEN

ADSC

ADATE

ADIF

ADIE

ADPS2

ADPS1

ADPS0

ADCSRA

Read/Write

R/W

Initial Value

0000

000

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