Datasheet

137
2586D–AVR–02/06
ATtiny25/45/85
20.7.5 ADCSRA – ADC Control and Status Register A
• Bit 7 – ADEN: ADC Enable
Writing this bit to one enables the ADC. 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 take 25 ADC clock cycles instead of the normal 13. This first conversion performs initializa-
tion of the ADC.
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.
Table 20-3. Input Channel Selections
MUX3..0
Single Ended
Input
Positive
Differential Input
Negative
Differential Input Gain
0000 ADC0 (PB5)
N/A
0001 ADC1 (PB2)
0010 ADC2 (PB4)
0011 ADC3 (PB3)
0100
N/A
ADC2 (PB4) ADC2 (PB4) 1x
0101
(1)
1. For offset calibration only . See Section “20.2” on page 125.
ADC2 (PB4) ADC2 (PB4) 20x
0110 ADC2 (PB4) ADC3 (PB3) 1x
0111 ADC2 (PB4) ADC3 (PB3) 20x
1000 ADC0 (PB5) ADC0 (PB5) 1x
1001 ADC0 (PB5) ADC0 (PB5) 20x
1010 ADC0 (PB5) ADC1 (PB2) 1x
1011 ADC0 (PB5) ADC1 (PB2) 20x
1100 1.1V/2.56V
N/A
1101 0V
1110 N/A
1111 ADC4
(2)
2. For Temperature Sensor
Bit 76543210
0x06 ADEN ADSC ADATE ADIF ADIE ADPS2 ADPS1 ADPS0 ADCSRA
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000