MEGA128CAN Datasheet, PDF (277/413 Pages) ATMEL Corporation – Microcontroller WITH 128K BYTES OF ISP FLASH AND CAN CONTROLLER

AT90CAN128
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:
ADC = ^V----^I--^N-----^â‹---¹---⁰----²---³--
V_REF
where V_IN is the voltage on the selected input pin and V_REF the selected voltage refer-
ence (see Table 101 on page 279 and Table 102 on page 280). 0x000 represents
analog ground, and 0x3FF represents the selected reference voltage minus one LSB.
If differential channels are used, the result is:
ADC = -⁽--^V----^P---^O----^S----–----^V----^N----^E---^G----⁾----^â‹---^G----^A----^I---^N-----^â‹---⁵---¹----²--
V_REF
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). Note that if the user wants to perform a quick polarity check of the result, it is
sufficient to read the MSB of the result (ADC9 in ADCH). If the bit is one, the result is
negative, and if this bit is zero, the result is positive. Figure 140 shows the decoding of
the differential input range.
Table 82 shows the resulting output codes if the differential input channel pair (ADCn -
ADCm) is selected with a reference voltage of V_REF.
Figure 140. Differential Measurement Range
Output Code
0x1FF
- V_REF
0x000
0x3FF ⁰
V_REF
Differential Input
Voltage (Volts)
4250E–CAN–12/04
0x200
277