Rainbow-electronics ATmega128L Manuel d'utilisateur télécharger pdf (Page 232)

232

ATmega128(L)

2467B–09/01

where V

is the voltage on the selected input pin and V

REF

the selected voltage refer-

ence (see

Table 96 on page 233 and Table 97 on page 234). 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, V

NEG

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). There are no leading 1's above the MSB / sign bit, even if the result is negative.

Figure 118 shows the decoding of the differential input range.

Table 95 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 118. Differential Measurement Range

ADC

1024⋅

REF

--------------------------=

ADC

POS

NEG

–()GAIN 512⋅⋅

REF

------------------------------------------------------------------------=

Output code

0x1FF

0x000

REF

/GAIN

Differential Input

voltage (Volts)

0x3FF

0x200

- V

REF

/GAIN

1 2 ... 227 228 229 230 231 232 233 234 235 236 237 ... 330 331

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Rainbow-electronics ATmega128L Manuel d'utilisateur Page 232

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