ATtiny5 datasheet(84/168 Pages) ATMEL

84 / 168 page

8127C–AVR–10/09

ATtiny4/5/9/10

Figure 13-1. Analog to Digital Converter Block Schematic

13.4 Starting a Conversion

Make sure the ADC is powered by clearing the ADC Power Reduction bit, PRADC, in the Power

Reduction Register, PRR (see “PRR – Power Reduction Register” on page 26).

A single conversion is started by writing a logical one to the ADC Start Conversion bit, ADSC.

This bit stays high as long as the conversion is in progress and will be cleared by hardware

when the conversion is completed. If a different data channel is selected while a conversion is in

progress, the ADC will finish the current conversion before performing the channel change.

Alternatively, a conversion can be triggered automatically by various sources. Auto Triggering is

enabled by setting the ADC Auto Trigger Enable bit, ADATE in ADCSRA. The trigger source is

selected by setting the ADC Trigger Select bits, ADTS in “ADCSRB – ADC Control and Status

occurs on the selected trigger signal, the ADC prescaler is reset and a conversion is started.

This provides a method of starting conversions at fixed intervals. If the trigger signal still is set

when the conversion completes, a new conversion will not be started. If another positive edge

occurs on the trigger signal during conversion, the edge will be ignored. Note that an interrupt

flag will be set even if the specific interrupt is disabled. A conversion can thus be triggered with-

out causing an interrupt. However, the interrupt flag must be cleared in order to trigger a new

conversion at the next interrupt event.

ADMUX

DECODER

8-BIT DATA BUS

ADCSRA

ADCL

TRIGGER

SELECT

VREF

PRESCALER

CONVERSION LOGIC

8-BIT DAC

ADCSRB

ADC3

ADC2

ADC1

ADC0

VCC

INPUT

MUX

ADC IRQ

SAMPLE & HOLD

COMPARATOR

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