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251
8210C–AVR–09/11
Atmel AVR XMEGA D
Figure 21-9.
Signed differential input (with gain), input range, and result representation.
Figure 21-10.
Signed single-ended and internal input, input range, and result representation.
Figure 21-11.
Unsigned single-ended and internal input, input range, and result representation.
21.7
Compare Function
The ADC has a built-in 12-bit compare function. The ADC compare register can hold a 12-bit
value that represents a threshold voltage. Each ADC channel can be configured to automatically
compare its result with this compare value to give an interrupt or event only when the result is
above or below the threshold.
All four ADC channels share the same compare register.
2047
2046
2045
...
3
2
1
0
-1
...
-2045
-2046
-2047
-2048
7FF
7FE
7FD
...
3
2
1
0
FFF
FFE
...
803
802
801
800
Dec
Hex
0111 1111 1111
0111 1111 1110
0111 1111 1101
...
0000 0000 0011
0000 0000 0010
0000 0000 0001
0000 0000 0000
1111 1111 1111
1111 1111 1110
...
1000 0000 0011
1000 0000 0010
1000 0000 0001
1000 0000 0000
Binary
0000 0111 1111 1111
0000 0111 1111 1110
0000 0111 1111 1101
...
0000 0000 0000 0011
0000 0000 0000 0010
0000 0000 0000 0001
0000 0000 0000 0000
1111 1111 1111 1111
1111 1111 1111 1110
...
1111 1000 0000 0011
1111 1000 0000 0010
1111 1000 0000 0001
1111 1000 0000 0000
16-bit result register
VREF
GAIN
-VREF
GAIN
0 V
VINN
RES
VINP
-2
2047
2046
2045
...
3
2
1
0
-1
-2
...
-2045
-2046
-2047
-2048
7FF
7FE
7FD
...
3
2
1
0
FFF
FFE
...
803
802
801
800
Dec
Hex
0111 1111 1111
0111 1111 1110
0111 1111 1101
...
0000 0000 0011
0000 0000 0010
0000 0000 0001
0000 0000 0000
1111 1111 1111
1111 1111 1110
...
1000 0000 0011
1000 0000 0010
1000 0000 0001
1000 0000 0000
Binary
0000 0111 1111 1111
0000 0111 1111 1110
0000 0111 1111 1101
...
0000 0000 0000 0011
0000 0000 0000 0010
0000 0000 0000 0001
0000 0000 0000 0000
1111 1111 1111 1111
1111 1111 1111 1110
...
1111 1000 0000 0011
1111 1000 0000 0010
1111 1000 0000 0001
1111 1000 0000 0000
16-bit result register
VREF
-VREF
0 V
VINP
VINN = GND
4095
4094
4093
...
203
202
201
200
FFF
FFE
FFD
...
0CB
0CA
0C9
0C8
Dec
Hex
1111 1111 1111
1111 1111 1110
1111 1111 1101
...
0000 1100 1011
0000 1100 1010
0000 1100 1001
0000 1100 1000
Binary
0000 1111 1111 1111
0000 1111 1111 1110
0000 1111 1111 1101
...
0000 0000 1100 1011
0000 0000 1100 1010
0000 0000 1100 1001
0000 0000 1100 1000
16-bit result register
V
VREF
VINN
Δ
−
=
2
GND
V
VREF
Δ
−
VINP
...
0
0
0000 0000 0000
0000 0000 0000 0000