Datasheet

Table Of Contents
PIC18F2525/2620/4525/4620
DS39626E-page 234 © 2008 Microchip Technology Inc.
20.1 Comparator Configuration
There are eight modes of operation for the compara-
tors, shown in Figure 20-1. Bits, CM2:CM0 of the
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
Section 26.0 “Electrical Characteristics”.
FIGURE 20-1: 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-
V
IN+
RA3/AN3/
Off (Read as ‘0’)
Comparators Reset
A
A
CM2:CM0 = 000
C2
RA1/AN1
VIN-
V
IN+
RA2/AN2/
Off (Read as ‘0’)
A
A
C1
VIN-
V
IN+
C1OUT
Two Independent Comparators
A
A
CM2:CM0 = 010
C2
VIN-
V
IN+
C2OUT
A
A
C1
VIN-
V
IN+
C1OUT
Two Common Reference Comparators
A
A
CM2:CM0 = 100
C2
VIN-
V
IN+
C2OUT
A
D
C2
VIN-
V
IN+
Off (Read as 0’)
One Independent Comparator with Output
D
D
CM2:CM0 = 001
C1
VIN-
V
IN+
C1OUT
A
A
C1
VIN-
V
IN+
Off (Read as ‘0’)
Comparators Off (POR Default Value)
D
D
CM2:CM0 = 111
C2
VIN-
V
IN+
Off (Read as ‘0’)
D
D
C1
VIN-
V
IN+
C1OUT
Four Inputs Multiplexed to Two Comparators
A
A
CM2:CM0 = 110
C2
VIN-
V
IN+
C2OUT
A
A
From VREF Module
CIS = 0
CIS = 1
CIS = 0
CIS = 1
C1
VIN-
V
IN+
C1OUT
Two Common Reference Comparators with Outputs
A
A
CM2:CM0 = 101
C2
VIN-
V
IN+
C2OUT
A
D
A = Analog Input, port reads zeros always D = Digital Input CIS (CMCON<3>) is the Comparator Input Switch
CV
REF
C1
VIN-
V
IN+
C1OUT
Two Independent Comparators with Outputs
A
A
CM2:CM0 = 011
C2
VIN-
V
IN+
C2OUT
A
A
RA5/AN4/SS/HLVDIN/C2OUT*
RA4/T0CKI/C1OUT*
VREF+
V
REF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
V
REF+
V
REF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
V
REF+
V
REF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
V
REF+
V
REF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
V
REF+
V
REF-/CVREF
RA0/AN0
RA3/AN3/
RA1/AN1
RA2/AN2/
V
REF+
V
REF-/CVREF
RA0/AN0
RA3/AN3/
V
REF+
RA1/AN1
RA2/AN2/
V
REF-/CVREF
RA4/T0CKI/C1OUT*
RA5/AN4/SS
/HLVDIN/C2OUT*
RA0/AN0
RA3/AN3/
V
REF+
RA1/AN1
RA2/AN2/
V
REF-/CVREF
RA4/T0CKI/C1OUT*
* Setting the TRISA<5:4> bits will disable the comparator outputs by configuring the pins as inputs.