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103

ATtiny26(L)

1477G–AVR–03/05

ADC Control and Status

• Bit 7 – ADEN: ADC Enable

Writing a logical “1” to this bit enables the ADC. By clearing this bit 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, a logical “1” must be written to this bit to start each conver-

sion. In Free Running mode, a logical “1” must be written to this bit to start the first

conversion. The first time ADSC has been written after the ADC has been enabled, or if

ADSC is written at the same time as the ADC is enabled, a dummy conversion will pre-

cede the initiated conversion. This dummy conversion performs initialization 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. When a dummy conversion precedes a real conversion,

ADSC will stay high until the real conversion completes. Writing a 0 to this bit has no

effect.

• Bit 5 – ADFR: ADC Free Running Select

When this bit is set (one) the ADC operates in Free Running mode. In this mode, the

ADC samples and updates the Data Registers continuously. Clearing this bit (zero) will

terminate Free Running mode.

• Bit 4 – ADIF: ADC Interrupt Flag

This bit is set (one) when an ADC conversion completes and the data registers are

updated. The ADC Conversion Complete Interrupt is executed if the ADIE bit and the I-

bit in SREG are set (one). ADIF is cleared by hardware when executing the correspond-

ing interrupt handling vector. Alternatively, ADIF is cleared by writing a logical one to the

flag. Beware that if doing a read-modify-write on ADCSR, a pending interrupt can be dis-

abled. This also applies if the SBI and CBI instructions are used.

• Bit 3 – ADIE: ADC Interrupt Enable

When this bit is set (one) and the I-bit in SREG is set (one), the ADC Conversion Com-

plete Interrupt is activated.

Bit 76543210

$06 ($26) ADEN ADSC ADFR ADIF ADIE ADPS2 ADPS1 ADPS0 ADCSR

Read/Write R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value00000000

Atmel ATtiny26 User Manual

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