ATmega16 datasheet(210/315 Pages) ATMEL

210 / 315 page

210

ATmega16(L)

2466E–AVR–10/02

ADC Conversion Result

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

IN is the voltage on the selected input pin and VREF the selected voltage refer-

ence (see Table 82 on page 211 and Table 83 on page 212). 0x000 represents analog

ground, and 0x3FF represents the selected reference voltage minus one LSB.

If differential channels are used, the result is

where V

POS is the voltage on the positive input pin, VNEG the voltage on the negative

input pin, GAIN the selected gain factor, and V

REF the selected voltage reference. The

result is presented 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 positive. Figure 111 shows the decoding of

the differential input range.

Table 81 shows the resulting output codes if the differential input channel pair (ADCn -

ADCm) is selected with a gain of GAIN and a reference voltage of V

REF.

Figure 111. Differential Measurement Range

ADC

1024

⋅

REF

--------------------------

ADC

PO S

NEG

–

() GAIN 512

⋅⋅

REF

------------------------------------------------------------------------

Output Code

0x1FF

0x000

REF/GAIN

Differential Input

Voltage (Volts)

0x3FF

0x200

- V

REF/GAIN

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