NEX ROBOTICS Fire Bird V ATMEGA2560 Software Manual page 99

7.2.4 ACSR – Analog Comparator Control and Status Register
Bit 7
ACD
Read / Write R/W
Initial Value 0
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
Comparator. When the bandgap reference 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. For more information see "Internal Voltage Reference" on page 62 of the ATMEGA2560
datasheet.
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.
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 ICIE1 bit in the Timer
Interrupt Mask Register (TIMSK1) 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 are shown in Table 7.4.
© NEX Robotics Pvt. Ltd. and ERTS Lab IIT Bombay, INDIA
6 5
ACBG ACO
R/W R
0 0
Fire Bird V ATMEGA2560 Software Manual
4 3
ACI ACIE ACIC
R/W R/W R/W
0 0
2 1 0
ACIS1 ACIS0
R/W R/W
0 0 0
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