Datasheet
221
ATmega169A/PA/329A/PA/649A/P/3290A/PA/6490A/P [DATASHEET]
8284E–AVR–02/2013
23.9.3 ADCL and ADCH – The ADC Data Register
23.9.3.1 ADLAR = 0
23.9.3.2 ADLAR = 1
When an ADC conversion is complete, the result is found in these two registers. When ADCL is read, the ADC
Data Register is not updated until ADCH is read. Consequently, if the result is left adjusted and no more than 8-bit
precision is required, it is sufficient to read ADCH. Otherwise, ADCL must be read first, then ADCH.
The ADLAR bit in ADMUX, and the MUXn bits in ADMUX affect the way the result is read from the registers. If
ADLAR is set, the result is left adjusted. If ADLAR is cleared (default), the result is right adjusted.
• ADC9:0: ADC Conversion Result
These bits represent the result from the conversion, as detailed in ”ADC Conversion Result” on page 216.
23.9.4 ADCSRB – ADC Control and Status Register B
• Bit 7 – Reserved
This bit is reserved for future use. To ensure compatibility with future devices, this bit must be written to zero when
ADCSRB is written.
• Bit 2:0 – ADTS[2:0:] ADC Auto Trigger Source
If ADATE in ADCSRA is written to one, the value of these bits selects which source will trigger an ADC conversion.
If ADATE is cleared, the ADTS[2:0] 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 (ADTS[2:0]=0) will not cause a trigger event, even if the ADC Interrupt Flag is set
.
Bit 151413121110 9 8
(0x79)
– – – – – – ADC9 ADC8 ADCH
(0x78) ADC7 ADC6 ADC5 ADC4 ADC3 ADC2 ADC1 ADC0 ADCL
76543210
Read/Write RRRRRRRR
RRRRRRRR
Initial Value 0 0 0 0 0 0 0 0
00000000
Bit 151413121110 9 8
(0x79) ADC9 ADC8 ADC7 ADC6 ADC5 ADC4 ADC3 ADC2 ADCH
(0x78) ADC1 ADC0
– – – – – – ADCL
76543210
Read/Write RRRRRRRR
RRRRRRRR
Initial Value 0 0 0 0 0 0 0 0
00000000
Bit 76543210
(0x7B)
– ACME – – – ADTS2 ADTS1 ADTS0 ADCSRB
Read/Write R R/W R R R R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0