![](http://datasheet.mmic.net.cn/90000/MR83C154CXXX-L16P883_datasheet_2373994/MR83C154CXXX-L16P883_137.png)
137
ATtiny25/45/85 [DATASHEET]
2586Q–AVR–08/2013
17.13.3
ADCL and ADCH – The ADC Data Register
17.13.3.1
ADLAR = 0
17.13.3.2
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.
Bits 9:0 - ADC[9:0]: ADC Conversion Result
17.13.4
ADCSRB – ADC Control and Status Register B
Bit 7 – BIN: Bipolar Input Mode
The gain stage is working in the unipolar mode as default, but the bipolar mode can be selected by writing the BIN
bit in the ADCSRB register. In the unipolar mode only one-sided conversions are supported and the voltage on the
positive input must always be larger than the voltage on the negative input. Otherwise the result is saturated to the
voltage reference. In the bipolar mode two-sided conversions are supported and the result is represented in the
two’s complement form. In the unipolar mode the resolution is 10 bits and the bipolar mode the resolution is 9 bits
+ 1 sign bit.
Bit 5 – IPR: Input Polarity Reversal
The Input Polarity mode allows software selectable differential input pairs and full 10 bit ADC resolution, in the uni-
polar input mode, assuming a pre-determined input polarity. If the input polarity is not known it is actually possible
to determine the polarity first by using the bipolar input mode (with 9 bit resolution + 1 sign bit ADC measurement).
And once determined, set or clear the polarity reversal bit, as needed, for a succeeding 10 bit unipolar
measurement.
Bit
151413
1211
10
9
8
––––––
ADC9
ADC8
ADCH
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADC1
ADC0
ADCL
76543210
Read/Write
RRRRRR
RR
RRRRRR
RR
Initial Value
00000000
Bit
15
14
13121110
9
8
ADC9
ADC8
ADC7
ADC6
ADC5
ADC4
ADC3
ADC2
ADCH
ADC1
ADC0
––––––
ADCL
76543210
Read/Write
RRRRRR
RR
RRRRRR
RR
Initial Value
00000000
Bit
7
6
543
21
0
BIN
ACME
IPR
–
ADTS2
ADTS1
ADTS0
ADCSRB
Read/Write
R/W
R
R/W
Initial Value
0