ATMEGA48_11 Datasheet, PDF (242/377 Pages) ATMEL Corporation – High performance, low power Atmel AVR 8-bit microcontroller Advanced RISC architecture

ATmega48/88/168
Table 23-1.
ACME
1
1
1
1
1
1
1
Analog comparator multiplexed input. (Continued)
ADEN
MUX2..0
Analog comparator negative input
0
001
ADC1
0
010
ADC2
0
011
ADC3
0
100
ADC4
0
101
ADC5
0
110
ADC6
0
111
ADC7
23.3 Register description
23.3.1 ADCSRB – ADC control and status register B
Bit
(0x7B)
Read/write
Initial value
7
6
5
4
3
2
1
0
–
ACME
–
–
–
ADTS2 ADTS1 ADTS0 ADCSRB
R
R/W
R
R
R
R/W
R/W
R/W
0
0
0
0
0
0
0
0
• 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 Comparator. For a detailed
description of this bit, see “Analog comparator multiplexed input” on page 241.
23.3.2
ACSR – Analog comparator control and status register
Bit
0x30 (0x50)
Read/write
Initial value
7
6
5
4
ACD
ACBG
ACO
ACI
R/W
R/W
R
R/W
0
0
N/A
0
3
ACIE
R/W
0
2
ACIC
R/W
0
1
ACIS1
R/W
0
0
ACIS0
R/W
0
ACSR
• 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 Comparator Interrupt must be
disabled by clearing the ACIE bit in ACSR. Otherwise an interrupt can occur when the bit is
changed.
• Bit 6 – ACBG: Analog comparator bandgap select
When this bit is set, a fixed bandgap reference voltage replaces the positive input to the Analog
Comparator. When this bit is cleared, AIN0 is applied to the positive input of the Analog Compar-
ator. When the bandgap reference voltage is used as input to the Analog Comparator, it will take
a certain time for the voltage to stabilize. If not stabilized, the first conversion may give a wrong
value. See “Internal voltage reference” on page 48.
• Bit 5 – ACO: Analog comparator output
The output of the Analog Comparator is synchronized and then directly connected to ACO. The
synchronization introduces a delay of 1 - 2 clock cycles.
2545T–AVR–05/11
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