ATA5771 ATMEL Corporation, ATA5771 Datasheet - Page 197

• Manufacturer Part Number: ATA5771
• Manufacturer: ATMEL Corporation

16.13 Register Description
16.13.1
8006G–AVR–01/08
ADMUX – ADC Multiplexer Selection Register
• Bit 7:6 – REFS1:REFS0: Reference Selection Bits
These bits select the voltage reference for the ADC, as shown in
Table 16-3.
If these bits are changed during a conversion, the change will not go in effect until this
conversion is complete (ADIF in ADCSR is set).
Special care should be taken when changing differential channels. Once a differential channel
has been selected the input stage may take a while to stabilize. It is therefore recommended to
force the ADC to perform a long conversion when changing multiplexer or voltage reference set-
tings. This can be done by first turning off the ADC, then changing reference settings and then
turn on the ADC. Alternatively, the first conversion results after changing reference settings
should be discarded.
If channels where differential gain is used ie. the gainstage, using V
AREF higher than (V
• Bits 5:0 – MUX5:0: Analog Channel and Gain Selection Bits
The value of these bits selects which combination of analog inputs are connected to the ADC. In
case of differential input, gain selection is also made with these bits. Selections on
page 146
the offset calibration selections are located. Selecting the single-ended channel ADC8 enables
the temperature measurement. See
changed during a conversion, the change will not go into effect until this conversion is complete
(ADIF in ADCSRA is set).
Special care should be taken when changing differential channels. Once a differential channel
has been selected the input stage may take a while to stabilize. It is therefore recommended to
force the ADC to perform a long conversion when changing multiplexer settings. This can be
Bit
0x07 (0x27)
Read/Write
Initial Value
REFS1
0
0
1
1
show values for single endid channels and where the differential channels as well as
Voltage Reference Selections for ADC
REFS1
R/W
7
0
REFS0
0
1
0
1
CC
- 1V) is not recommended, as this will affect ADC accuracy.
REFS0
R/W
6
0
Voltage Reference Selection
V
External voltage reference at PA0 (AREF) pin.
Internal voltage reference turned off
Internal 1.1V voltage reference
Reserved
CC
used as analog reference, disconnected from PA0 (AREF)
MUX5
R/W
5
0
Table 16-4 on page 146
MUX4
R/W
4
0
MUX3
R/W
3
0
MUX2
R/W
2
0
Table
for details. If these bits are
ATtiny24/44/84
CC
MUX1
R/W
16-3.
1
0
or an optional external
MUX0
R/W
0
0
Table 16-4 on
ADMUX
145