ATmega644 Atmel Corporation, ATmega644 Datasheet - Page 246

• Manufacturer Part Number: ATmega644
• Manufacturer: Atmel Corporation

Specifications of ATmega644

• Flash (kbytes): 64 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 32
• Ext Interrupts: 32
• Usb Speed: No
• Usb Interface: No
• Spi: 3
• Twi (i2c): 1
• Uart: 1
• 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): 2048
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 6
• Input Capture Channels: 1
• Pwm Channels: 6
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

21.8
246
ADC Conversion Result
ATmega644
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 21-3 on page 248
0x3FF represents the selected reference voltage minus one LSB.
If differential channels are used, the result is
where V
GAIN the selected gain factor, and V
in two’s complement form, from 0x200 (-512d) through 0x1FF (+511d). Note that if the user
wants to perform a quick polarity check of the results, it is sufficient to read the MSB of the result
(ADC9 in ADCH). If this bit is one, the result is negative, and if this bit is zero, the result is posi-
tive.
Table 21-2
is selected with a gain of GAIN and a reference voltage of V
Figure 21-14
IN
POS
is the voltage on the selected input pin and V
shows the resulting output codes if the differential input channel pair (ADCn - ADCm)
is the voltage on the positive input pin, V
shows the decoding of the differential input range.
and
ADC
Table 21-4 on page
=
(
----------------------------------------------------------------------- -
V
ADC
POS
REF
the selected voltage reference. The result is presented
–
=
V
NEG
V
--------------------------
V
IN
REF
V
) GAIN 512
⋅
REF
⋅
1024
248). 0x000 represents analog ground, and
NEG
REF
⋅
the voltage on the negative input pin,
REF
the selected voltage reference (see
.
2593N–AVR–07/10