
232
8018P–AVR–08/10
ATmega169P
22.9.3
ADCL and ADCH – ADC Data Register
22.9.3.1
ADLAR = 0
22.9.3.2
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
Table 22-5.
ADC Prescaler Selections
ADPS2
ADPS1
ADPS0
Division Factor
000
2
001
2
010
4
011
8
100
16
101
32
110
64
111
128
Bit
151413121110
9
8
(0x79)
–
ADC9
ADC8
ADCH
(0x78)
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
ADCL
765
43
21
0
Read/Write
RR
R
RR
R
Initial Value
0
000
00
0
Bit
151413121110
9
8
ADC9
ADC8
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADCH
ADC1
ADC0
–
ADCL
765
43
21
0
Read/Write
RR
R
RR
R
Initial Value
0
000
00
0