Datasheet

121
2586D–AVR–02/06
ATtiny25/45/85
19. Analog Comparator
The Analog Comparator compares the input values on the positive pin AIN0 and negative 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 can trigger a separate inter-
rupt, exclusive to the Analog Comparator. The user can select Interrupt triggering on comparator
output rise, fall or toggle. A block diagram of the comparator and its surrounding logic is shown
in Figure 19-1.
Figure 19-1. Analog Comparator Block Diagram
(2)
Notes: 1. See Table 19-2 on page 123.
2. Refer to Figure 1-1 on page 2 and Table 12-5 on page 62 for Analog Comparator pin
placement.
19.0.1 ADCSRB – ADC Control and Status Register B
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 122.
19.0.2 ACSR – Analog Comparator Control and Status Register
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
ACBG
BANDGAP
REFERENCE
ADC MULTIPLEXER
OUTPUT
ACME
ADEN
(1)
Bit 7 6543210
0x03
BIN ACME IPR ADTS2 ADTS1 ADTS0 ADCSRB
Read/Write R R/W R R R R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
Bit 76543210
0x08 ACD ACBG ACO ACI ACIE ACIS1 ACIS0 ACSR
Read/Write R/W R/W R R/W R/W R R/W R/W
Initial Value 0 0 N/A 0 0 0 0 0