Atmel Xplained Pro Evaluation Kit for the ATSAMD21J18A Microcontroller ATSAMD21-XPRO ATSAMD21-XPRO Data Sheet

875

Atmel | SMART SAM D21 [DATASHEET]

Atmel-42181C–SAM-D21_Datasheet–07/2014

Not applicable.

Each comparator has one positive input and one negative input. Each positive input may be chosen from a selection of 
analog input pins. Each negative input may be chosen from a selection of analog input pins or internal inputs, such as a 
bandgap reference voltage. The digital output from the comparator is one when the difference between the positive and 
the negative input voltage is positive, and zero otherwise.

The individual comparators can be used independently (normal mode) or grouped in pairs to generate a window 
comparison (window mode).

Before enabling the AC, the input and output events must be configured in the Event Control register (

). These 

settings cannot be changed while the AC is enabled.

Each individual comparator must also be configured by its respective Comparator Control register (

) before 

that comparator is enabled. These settings cannot be changed while the comparator is enabled.

z

Select the desired measurement mode with COMPCTRLx.SINGLE. See 

 for more details

z

Select the desired hysteresis with COMPCTRLx.HYST. See 

 for more details

z

Select the comparator speed versus power with COMPCTRLx.SPEED. See 

 for more details

z

Select the interrupt source with COMPCTRLx.INTSEL

z

Select the positive and negative input sources with the COMPCTRLx.MUXPOS and 
COMPCTRLx.MUXNEG bits. See section 

 for more details

z

Select the filtering option with COMPCTRLx.FLEN

The AC is enabled by writing a one to the Enable bit in the Control A register (CTRLA.ENABLE). The individual 
comparators must be also enabled by writing a one to the Enable bit in the Comparator x Control registers 
(COMPCTRLx.ENABLE). The AC is disabled by writing a zero to CTRLA.ENABLE. This will also disable the individual 
comparators, but will not clear their COMPCTRLx.ENABLE bits.

The AC is reset by writing a one to the Software Reset bit in the Control A register (CTRLA.SWRST). All registers in the 
AC, except DEBUG, will be reset to their initial state, and the AC will be disabled. Refer to the 

 register for details.

Each comparator channel can be in one of two different measurement modes, determined by the Single bit in the 
Comparator x Control register (COMPCTRLx.SINGLE):

z

Continuous measurement

z

Single-shot

After being enabled, a start-up delay is required before the result of the comparison is ready. This start-up time is 
measured automatically to account for environmental changes, such as temperature or voltage supply level, and is 
specified in 

. 

During the start-up time, the COMP output is not available. If the supply voltage is below 2.5V, the start-up time is also 
dependent on the voltage doubler. If the supply voltage is guaranteed to be above 2.5V, the voltage doubler can be 
disabled by writing the Low-Power Mux bit in the Control A register (CTRLA.LPMUX) to one.