
PIC18F2X1X/4X1X
DS39636D-page 224
2009 Microchip Technology Inc.
19.1
Comparator Configuration
There are eight modes of operation for the compara-
CMCON register are used to select these modes. The
TRISA register controls the data direction of the com-
parator pins for each mode. If the Comparator mode is
changed, the comparator output level may not be valid
for the specified mode change delay shown in
FIGURE 19-1:
COMPARATOR I/O OPERATING MODES
Note:
Comparator interrupts should be disabled
during a Comparator mode change;
otherwise, a false interrupt may occur.
C1
RA0/AN0
VIN-
VIN+
RA3/AN3/
Off (Read as ‘0’)
Comparators Reset
A
CM2:CM0 = 000
C2
RA1/AN1
VIN-
VIN+
RA2/AN2/
Off (Read as ‘0’)
A
C1
VIN-
VIN+
C1OUT
Two Independent Comparators
A
CM2:CM0 = 010
C2
VIN-
VIN+
C2OUT
A
C1
VIN-
VIN+
C1OUT
Two Common Reference Comparators
A
CM2:CM0 = 100
C2
VIN-
VIN+
C2OUT
A
D
C2
VIN-
VIN+
Off (Read as ‘0’)
One Independent Comparator with Output
D
CM2:CM0 = 001
C1
VIN-
VIN+
C1OUT
A
C1
VIN-
VIN+
Off (Read as ‘0’)
Comparators Off (POR Default Value)
D
CM2:CM0 = 111
C2
VIN-
VIN+
Off (Read as ‘0’)
D
C1
VIN-
VIN+
C1OUT
Four Inputs Multiplexed to Two Comparators
A
CM2:CM0 = 110
C2
VIN-
VIN+
C2OUT
A
From VREF Module
CIS = 0
CIS = 1
CIS = 0
CIS = 1
C1
VIN-
VIN+
C1OUT
Two Common Reference Comparators with Outputs
A
CM2:CM0 = 101
C2
VIN-
VIN+
C2OUT
A
D
A = Analog Input, port reads zeros always
D = Digital Input
CIS (CMCON<3>) is the Comparator Input Switch
CVREF
C1
VIN-
VIN+
C1OUT
Two Independent Comparators with Outputs
A
CM2:CM0 = 011
C2
VIN-
VIN+
C2OUT
A
RA5/AN4/SS/HLVDIN/C2OUT*
RA4/T0CKI/C1OUT*
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
VREF+
VREF-/CVREF
RA0/AN0
RA3/AN3/
VREF+
RA1/AN1
RA2/AN2/
VREF-/CVREF
RA4/T0CKI/C1OUT*
RA5/AN4/SS/HLVDIN/C2OUT*
RA0/AN0
RA3/AN3/
VREF+
RA1/AN1
RA2/AN2/
VREF-/CVREF
RA4/T0CKI/C1OUT*
* Setting the TRISA<5:4> bits will disable the comparator outputs by configuring the pins as inputs.