Rainbow Electronics ATmega64M1 - Manual (Page 256)

256
8209A–AVR–08/09
ATmega16M1/32M1/64M1
24. AC – Analog Comparator
24.1 Features
• 4 Analog Comparators
• High Speed Clocked Comparators
• +/-30mV Hysteresys
• 4 reference levels
• Generation of Configurable Interrupts
24.2 Overview
The ATmega16M1/32M1/64M1 features 4 fast analog comparators. The Analog Comparator
compares the input values on the positive pin ACMPx and negative pin ACMPM or ACMPMx.
Each comparator has a dedicated input on the positive input, and the negative input of each
comparator can be configured as:
• a steady value among the 4 internal reference levels defined by the Vref selected thanks to
the REFS1:0 bits in ADMUX register.
• a value generated from the internal DAC
• an external analog input ACMPMx.
When the voltage on the positive ACMPn pin is higher than the voltage selected by the ACnM
multiplexer on the negative input, the Analog Comparator output, ACnO, is set.
The comparator is a clocked comparator. A new comparison is done on the falling edge of
CLK
I/O
or CLK
I/O
/2 ( Depending on ACCKDIV fit of ACSR register, See “ACSR – Analog Com-
parator Status Register” on page 262. ).
Each comparator can trigger a separate interrupt, exclusive to the Analog Comparator. In addi-
tion, the user can select Interrupt triggering on comparator output rise, fall or toggle.
The interrupt flags can also be used to synchronize ADC or DAC conversions.
Moreover, the comparator’s output of the comparator 1 can be set to trigger the Timer/Counter1
Input Capture function.
A block diagram of the four comparators and their surrounding logic is shown in Figure 24-1 .