
465
42073A-MCU Wireless-02/13
ATmega2564/1284/644RFR2
MUX5:0
Single Ended
Input
Positive Differential
Input
Negative Differential
Input
Gain
111101
SRAM Back-bias Voltage VDRTBBN
111110
Reserved
N/A
111111
Reserved
Note:
1. EVDD measurement is not available in ATmega128RFA1.
Bits 2:0 – ADTS2:0: ADC Auto Trigger Source
If ADATE in ADCSRA is written to one, the value of these bits selects which source will
trigger an A/D conversion. If ADATE is cleared, the ADTS2:0 settings will have no
effect. A conversion will be triggered by the rising edge of the selected Interrupt Flag.
Note that switching from a trigger source that is cleared, to a trigger source that is set,
will generate a positive edge on the trigger signal. If ADEN in ADCSRA is set, this will
start a conversion. Switching to Free Running mode (ADTS2:0=0) will not cause a
trigger event, even if the ADC Interrupt Flag is set.
Table 27-13. ADC Auto Trigger Source Selections
ADTS2
ADTS1
ADTS0
Trigger Source
0
Free Running mode
0
1
Analog Comparator
0
1
0
External Interrupt Request 0
0
1
Timer/Counter0 Compare Match A
1
0
Timer/Counter0 Overflow
1
0
1
Timer/Counter1 Compare Match B
1
0
Timer/Counter1 Overflow
1
Timer/Counter1 Capture Event
27.12.3 ADCSRA – ADC Control and Status Register A
Bit
7
6
5
4
3
2
1
0
NA ($7A)
ADEN
ADSC
ADATE
ADIF
ADIE
ADPS2
ADPS1
ADPS0
ADCSRA
Read/Write
R/W
Initial Value
0
Bit 7 – ADEN: ADC Enable
Writing this bit to one enables the ADC. The AVDD supply voltage will also be enabled
if not already available. By writing it to zero, the ADC is turned off. Turning the ADC off
while a conversion is in progress will terminate this conversion.
Bit 6 – ADSC: ADC Start Conversion
In Single Conversion mode, write this bit to one to start each conversion. In Free
Running mode, write this bit to one to start the first conversion. The first conversion
after ADSC has been written after the ADC has been enabled, or if ADSC is written at
the same time as the ADC is enabled, will include a start-up time to initialize the analog
blocks of the ADC. The start-up time is defined by the ADSUT bits of register ADCSRC.
ADSC will read as one as long as a conversion is in progress. When the conversion is
complete, it returns to zero. Writing zero to this bit has no effect.