
181
ATmega8A [DATASHEET]
8159E–AVR–02/2013
Bit 4 – ACI: Analog Comparator Interrupt Flag
This bit is set by hardware when a comparator output event triggers the interrupt mode defined by ACIS1 and
ACIS0. The Analog Comparator Interrupt routine is executed if the ACIE bit is set and the I-bit in SREG is set. ACI
is cleared by hardware when executing the corresponding interrupt Handling Vector. Alternatively, ACI is cleared
by writing a logic one to the flag.
Bit 3 – ACIE: Analog Comparator Interrupt Enable
When the ACIE bit is written logic one and the I-bit in the Status Register is set, the Analog Comparator interrupt is
activated. When written logic zero, the interrupt is disabled.
Bit 2 – ACIC: Analog Comparator Input Capture Enable
When written logic one, this bit enables the Input Capture function in Timer/Counter1 to be triggered by the Analog
Comparator. The comparator output is in this case directly connected to the Input Capture front-end logic, making
the comparator utilize the noise canceler and edge select features of the Timer/Counter1 Input Capture interrupt.
When written logic zero, no connection between the Analog Comparator and the Input Capture function exists. To
make the comparator trigger the Timer/Counter1 Input Capture interrupt, the TICIE1 bit in the Timer Interrupt Mask
Register (TIMSK) must be set.
Bits 1,0 – ACIS1, ACIS0: Analog Comparator Interrupt Mode Select
These bits determine which comparator events that trigger the Analog Comparator interrupt. The different settings
When changing the ACIS1/ACIS0 bits, the Analog Comparator Interrupt must be disabled by clearing its Interrupt
Enable bit in the ACSR Register. Otherwise an interrupt can occur when the bits are changed.
Table 22-2.
ACIS1/ACIS0 Settings
ACIS1
ACIS0
Interrupt Mode
0
Comparator Interrupt on Output Toggle
01
Reserved
1
0
Comparator Interrupt on Falling Output Edge
1
Comparator Interrupt on Rising Output Edge