ATmega128A Atmel Corporation, ATmega128A Datasheet - Page 245

• Manufacturer Part Number: ATmega128A
• Manufacturer: Atmel Corporation

Specifications of ATmega128A

• Flash (kbytes): 128 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 53
• Ext Interrupts: 8
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Uart: 2
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 4
• Eeprom (bytes): 4096
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 4
• Output Compare Channels: 8
• Input Capture Channels: 2
• Pwm Channels: 7
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

23.9
23.9.1
8151H–AVR–02/11
Register Description
ADMUX - ADC Multiplexer Selection Register
Table 23-2.
Example:
ADMUX = 0xED (ADC3 - ADC2, 10x gain, 2.56V reference, left adjusted result)
Voltage on ADC3 is 300 mV, voltage on ADC2 is 500 mV.
ADCR = 512 × 10 × (300 - 500) / 2560 = -400 = 0x270
ADCL will thus read 0x00, and ADCH will read 0x9C. Writing zero to ADLAR right adjusts the
result: ADCL = 0x70, ADCH = 0x02.
• 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 23-3.
Bit
Read/Write
Initial Value
V
V
V
:.
V
V
V
:.
V
V
V
REFS1
ADCn
ADCm
ADCm
ADCm
ADCm
ADCm
ADCm
ADCm
ADCm
0
0
1
1
+ 511/512 V
+ 511/512 V
+ 1/512 V
- 1/512 V
- 511/512 V
- V
+ V
REF
REF
REFS0
/GAIN
/GAIN
Correlation Between Input Voltage and Output Codes
Voltage Reference Selections for ADC
0
1
0
1
REFS1
REF
REF
R/W
7
0
REF
REF
REF
/GAIN
/GAIN
/GAIN
/GAIN
/GAIN
Voltage Reference Selection
AREF, Internal Vref turned off
AVCC with external capacitor at AREF pin
Reserved
Internal 2.56V Voltage Reference with external capacitor at AREF pin
REFS0
R/W
6
0
ADLAR
R/W
5
0
Read code
0x1FF
0x1FF
0x1FE
0x3FF
0x001
0x000
0x201
0x200
MUX4
R/W
4
0
:.
:.
MUX3
R/W
3
0
Corresponding decimal value
511
511
510
:.
1
0
-1
:.
-511
-512
MUX2
R/W
2
0
Table
MUX1
ATmega128A
R/W
1
0
23-3. If these bits are
MUX0
R/W
0
0
ADMUX
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