ATA6612 Datasheet, PDF (277/364 Pages) ATMEL Corporation – Microcontroller with LIN Transceiver, 5V Regulator and Watchdog

ATA6612/ATA6613
6.21.6
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---⁴--
V_REF
where V_IN is the voltage on the selected input pin and V_REF the selected voltage reference (see
Table 6-98 on page 277 and Table 6-99 on page 278). 0x000 represents analog ground, and
0x3FF represents the selected reference voltage minus one LSB.
6.21.6.1
ADC Multiplexer Selection Register – ADMUX
Bit
7
6
5
4
REFS1 REFS0 ADLAR
–
Read/Write
R/W
R/W
R/W
R
Initial Value
0
0
0
0
3
MUX3
R/W
0
2
MUX2
R/W
0
1
MUX1
R/W
0
0
MUX0
R/W
0
ADMUX
• Bit 7:6 – REFS1:0: Reference Selection Bits
These bits select the voltage reference for the ADC, as shown in Table 6-98. If these bits are
changed during a conversion, the change will not go in effect until this conversion is
complete (ADIF in ADCSRA is set). The internal voltage reference options may not be used
if an external reference voltage is being applied to the AREF pin.
Table 6-98. Voltage Reference Selections for ADC
REFS1 REFS0 Voltage Reference Selection
0
0
AREF, Internal V_ref turned off
0
1
AV_CC with external capacitor at AREF pin
1
0 Reserved
1
1 Internal 1.1V Voltage Reference with external capacitor at AREF pin
• Bit 5 – ADLAR: ADC Left Adjust Result
The ADLAR bit affects the presentation of the ADC conversion result in the ADC Data Reg-
ister. Write one to ADLAR to left adjust the result. Otherwise, the result is right adjusted.
Changing the ADLAR bit will affect the ADC Data Register immediately, regardless of any
ongoing conversions. For a complete description of this bit (see “The ADC Data Register –
ADCL and ADCH” on page 280).
• Bit 4 – Res: Reserved Bit
This bit is an unused bit in the ATA6612/ATA6613, and will always read as zero.
• Bits 3:0 – MUX3:0: Analog Channel Selection Bits
The value of these bits selects which analog inputs are connected to the ADC. See Table
6-99 on page 278 for details. If these bits are changed during a conversion, the change will
not go in effect until this conversion is complete (ADIF in ADCSRA is set).
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