Datasheet

135
7701F–AVR–10/12
Atmel ATtiny24/44/84 [Preliminary]
17.2 Register Description
17.2.1 ADCSRB – ADC Control and Status Register B
• Bit 6 – ACME: Analog Comparator Multiplexer Enable
When this bit is written logical 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 writ-
ten logical 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 134.
17.2.2 ACSR – Analog Comparator Control and Status Register
• Bit 7 – ACD: Analog Comparator Disable
When this bit is written logical 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 ana-
log comparator. When this bit is cleared, AIN0 is applied to the positive input of the analog
comparator.
• 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 one to two clock cycles.
Table 17-1. Analog Comparator Multiplexed Input
ACME ADEN MUX4..0 Analog Comparator Negative Input
0x xxAIN1
11 xxAIN1
1 0 00000 ADC0
1 0 00001 ADC1
1 0 00010 ADC2
1 0 00011 ADC3
1 0 00100 ADC4
1 0 00101 ADC5
1 0 00110 ADC6
1 0 00111 ADC7
Bit 76543210
0x03 (0x23)
BIN ACME – ADLAR – ADTS2 ADTS1 ADTS0 ADCSRB
Read/Write R/W R/W R R/w R R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
0x08 (0x28) ACD ACBG ACO ACI ACIE ACIC ACIS1 ACIS0 ACSR
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 N/A 0 0 0 0 0