ATMEGA325-16AJ ATMEL [ATMEL Corporation], ATMEGA325-16AJ Datasheet - Page 189

• Manufacturer Part Number: ATMEGA325-16AJ
• Description: 8-bit Microcontroller with In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Analog Comparator
ADC Control and Status
Register B – ADCSRB
Analog Comparator Control
and Status Register – ACSR
2570A–AVR–09/04
The Analog Comparator compares the input values on the positive pin AIN0 and nega-
tive pin AIN1. When the voltage on the positive pin AIN0 is higher than the voltage on
the negative pin AIN1, the Analog Comparator output, ACO, is set. The comparator’s
output can be set to trigger the Timer/Counter1 Input Capture function. In addition, the
comparator can trigger a separate interrupt, exclusive to the Analog Comparator. The
user can select Interrupt triggering on comparator output rise, fall or toggle. A block dia-
gram of the comparator and its surrounding logic is shown in Figure 82.
The Power Reduction ADC bit, PRADC, in “Power Reduction Register” on page 35 must
be disabled by writing a logical zero to be able to use the ADC module.
Figure 82. Analog Comparator Block Diagram
Notes:
• Bit 6 – ACME: Analog Comparator Multiplexer Enable
When this bit is written logic one and the ADC is switched off (ADEN in ADCSRA is
zero), the ADC multiplexer selects the negative input to the Analog Comparator. When
this bit is written logic zero, AIN1 is applied to the negative input of the Analog Compar-
ator. For a detailed description of this bit, see “Analog Comparator Multiplexed Input” on
page 192.
• Bit 7 – ACD: Analog Comparator Disable
When this bit is written logic one, the power to the Analog Comparator is switched off.
This bit can be set at any time to turn off the Analog Comparator. This will reduce power
consumption in Active and Idle mode. When changing the ACD bit, the Analog Compar-
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
ADC MULTIPLEXER
REFERENCE
ACME
ADEN
OUTPUT
BANDGAP
1. See Table 84 on page 192.
2. Refer to Figure 1 on page 2, Figure 2 on page 3, and “Alternate Functions of Port E”
on page 63 for Analog Comparator pin placement.
(1)
ACD
ACBG
R/W
R
7
0
7
–
0
ACBG
ACME
R/W
R/W
6
0
6
0
ACO
N/A
R
5
R
5
–
0
ATmega325/3250/645/6450
R/W
ACI
4
0
R
4
–
0
(2)
ACIE
R/W
3
0
R
3
–
0
ADTS2
ACIC
R/W
R/W
2
0
2
0
ACIS1
ADTS1
R/W
R/W
1
0
1
0
ACIS0
ADTS0
R/W
R/W
0
0
0
0
ADCSRB
ACSR
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