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262
8272E–AVR–04/2013
ATmega164A/PA/324A/PA/644A/PA/1284/P
23.9.3
ADCL and ADCH – The ADC Data Register
ADLAR = 0
ADLAR = 1
When an ADC conversion is complete, the result is found in these two registers. If differential
channels are used, the result is presented in two’s complement form.
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
23.9.4
ADCSRB – ADC Control and Status Register B
10
0
16
10
1
32
11
0
64
11
1
128
Table 23-5.
ADC prescaler selections. (Continued)
ADPS2
ADPS1
ADPS0
Division factor
Bit
15
14131211
10
9
8
–
ADC9
ADC8
ADCH
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
ADCL
765432
10
Read/Write
RRRR
Initial Value
000000
00
000000
00
Bit
15
14131211
10
9
8
ADC9
ADC8
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADCH
ADC1
ADC0
–
ADCL
765432
10
Read/Write
RRRR
Initial Value
000000
00
000000
00
Bit
7
65
4
3
21
0
–
ACME
–
ADTS2
ADTS1
ADTS0
ADCSRB
Read/Write
R
R/W
R
R/W
Initial Value
0