ATMEGA48-20AI Atmel, ATMEGA48-20AI Datasheet - Page 254

• Manufacturer Part Number: ATMEGA48-20AI
• Description: IC AVR MCU 4K 5V 20MHZ 32-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA48-20AI

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 23
• Program Memory Size: 4KB (2K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-TQFP, 32-VQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: ATMEGA48-24AI; ATMEGA48-24AI

23.7
23.8
23.8.1
254
ADC Conversion Result
Register Description
ATmega48/88/168
ADMUX – ADC Multiplexer Selection Register
After the conversion is complete (ADIF is high), the conversion result can be found in the ADC
Result Registers (ADCL, ADCH).
For single ended conversion, the result is
where V
Table 23-2 on page 254
0x3FF represents the selected reference voltage minus one LSB.
• Bit 7:6 – REFS1:0: Reference Selection Bits
These bits select the voltage reference for the ADC, as shown in
changed during a conversion, the change will not go in effect until this conversion is complete
(ADIF in ADCSRA is set). The internal voltage reference options may not be used if an external
reference voltage is being applied to the AREF pin.
Table 23-2.
• Bit 5 – ADLAR: ADC Left Adjust Result
The ADLAR bit affects the presentation of the ADC conversion result in the ADC Data Register.
Write one to ADLAR to left adjust the result. Otherwise, the result is right adjusted. Changing the
ADLAR bit will affect the ADC Data Register immediately, regardless of any ongoing conver-
sions. For a complete description of this bit, see
page
• Bit 4 – Res: Reserved Bit
This bit is an unused bit in the ATmega48/88/168, and will always read as zero.
• Bits 3:0 – MUX3:0: Analog Channel Selection Bits
Bit
(0x7C)
Read/Write
Initial Value
REFS1
0
0
1
1
257.
IN
is the voltage on the selected input pin and V
REFS0
REFS1
Voltage Reference Selections for ADC
R/W
0
1
0
1
7
0
REFS0
Voltage Reference Selection
AREF, Internal V
AV
Reserved
Internal 1.1V Voltage Reference with external capacitor at AREF pin
R/W
6
0
and
CC
with external capacitor at AREF pin
Table 23-3 on page
ADLAR
R/W
5
0
ADC
ref
turned off
R
0
4
–
=
V
--------------------------
MUX3
IN
R/W
“ADCL and ADCH – The ADC Data Register” on
V
3
0
⋅
REF
1024
255). 0x000 represents analog ground, and
MUX2
R/W
REF
2
0
the selected voltage reference (see
MUX1
R/W
1
0
Table
MUX0
R/W
0
0
23-2. If these bits are
ADMUX
2545S–AVR–07/10