attiny25v ATMEL Corporation, attiny25v Datasheet - Page 140

• Manufacturer Part Number: attiny25v
• Description: Microcontroller With 2/4/8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

17.13.2
140
ATtiny25/45/85
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.
• Bit 5 – ADATE: ADC Auto Trigger Enable
When this bit is written to one, Auto Triggering of the ADC is enabled. The ADC will start a con-
version on a positive edge of the selected trigger signal. The trigger source is selected by setting
the ADC Trigger Select bits, ADTS in ADCSRB.
• Bit 4 – ADIF: ADC Interrupt Flag
This bit is set when an ADC conversion completes and the data registers are updated. The ADC
Conversion Complete Interrupt is executed if the ADIE bit and the I-bit in SREG are set. ADIF is
cleared by hardware when executing the corresponding interrupt handling vector. Alternatively,
ADIF is cleared by writing a logical one to the flag. Beware that if doing a Read-Modify-Write on
ADCSRA, a pending interrupt can be disabled. This also applies if the SBI and CBI instructions
are used.
• Bit 3 – ADIE: ADC Interrupt Enable
When this bit is written to one and the I-bit in SREG is set, the ADC Conversion Complete Inter-
rupt is activated.
• Bits 2:0 – ADPS2:0: ADC Prescaler Select Bits
These bits determine the division factor between the system clock frequency and the input clock
to the ADC.
Table 17-5.
Bit
0x06
Read/Write
Initial Value
ADPS2
0
0
0
0
1
ADC Prescaler Selections
7
R/W
0
ADEN
6
R/W
0
ADSC
ADPS1
0
0
1
1
0
5
R/W
0
ADATE
4
R/W
0
ADIF
ADPS0
0
1
0
1
0
3
R/W
0
ADIE
2
R/W
0
ADPS2
1
R/W
0
ADPS1
Division Factor
16
2
2
4
8
0
R/W
0
ADPS0
2586K–AVR–01/08
ADCSRA