ATMEga64L ATMEL Corporation, ATMEga64L Datasheet - Page 242

• Manufacturer Part Number: ATMEga64L
• Description: 8-bit AVR Microcontroller with 64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL Corporation

ADC Conversion Result
242
ATmega64(L)
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
ence (see Table 97 on page 243 and Table 98 on page 244). 0x000 represents analog
ground, and 0x3FF represents the selected reference voltage minus one LSB.
If differential channels are used, the result is
where V
input pin, GAIN the selected gain factor, and V
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 121 shows the decoding of
the differential input range.
Table 96 shows the resulting output codes if the differential input channel pair (ADCn -
Figure 121. Differential Measurement Range
ADCm) is selected with a gain of GAIN and a reference voltage of V
- V
REF
/GAIN
IN
POS
is the voltage on the selected input pin and V
is the voltage on the positive input pin, V
ADC
=
(
----------------------------------------------------------------------- -
Output Code
V
0x3FF
POS
0x1FF
0x000
ADC
–
V
0
0x200
NEG
=
V
V
--------------------------
REF
) GAIN 512
IN
⋅
V
⋅
REF
REF
1024
the selected voltage reference. The
⋅
NEG
REF
the voltage on the negative
the selected voltage refer-
V
REF
REF
/GAIN Differential Input
.
Voltage (Volts)
2490G–AVR–03/04