atmega323l ATMEL Corporation, atmega323l Datasheet - Page 128

• Manufacturer Part Number: atmega323l
• Description: Atmega323 8-bit Avr Microcontroller With 32k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

Operation
128
ATmega323(L)
Figure 60. Analog to Digital Converter Block Schematic
The ADC converts an analog input voltage to a 10-bit digital value through successive
approximation. The minimum value represents AGND and the maximum value repre-
sents the voltage on the AREF pin minus 1 LSB. Optionally, AVCC or an internal 2.56V
reference voltage may be connected to the AREF pin by writing to the REFSn bits in the
ADMUX Register. The internal voltage reference may thus be decoupled by an external
capacitor at the AREF pin to improve noise immunity.
The analog input channel is selected by writing to the MUX bits in ADMUX. Any of the
eight ADC input pins ADC7..0, as well as AGND and a fixed bandgap voltage reference
of nominally 1.22 V (V
The ADC can operate in two modes – Single Conversion and Free Running mode. In
Single Conversion mode, each conversion will have to be initiated by the user. In Free
Running mode, the ADC is constantly sampling and updating the ADC Data Register.
The ADFR bit in ADCSR selects between the two available modes.
AREF
AGND
AVCC
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
INTERNAL 2.56 V
1.22 V BANDGAP
REFERENCE
REFERENCE
8-BIT DATA BUS
INPUT
MUX
BG
ADC MULTIPLEXER
), can be selected as single ended inputs to the ADC.
SELECT (ADMUX)
MUX DECODER
10-BIT DAC
ADC CTRL. & STATUS
REGISTER (ADCSR)
ADC CONVERSION
COMPLETE IRQ
CONVERSION LOGIC
PRESCALER
15
SAMPLE & HOLD
COMPARATOR
ADC DATA REGISTER
+
-
(ADCH/ADCL)
ADC MULTIPLEXER
OUTPUT
1457G–AVR–09/03
0