Datasheet

PIC18F2455/2550/4455/4550
DS39632E-page 276 © 2009 Microchip Technology Inc.
22.1 Comparator Configuration
There are eight modes of operation for the compara-
tors, shown in Figure 22-1. Bits, CM2:CM0 of the
CMCON register, are used to select these modes. The
TRISA register controls the data direction of the
comparator 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 28.0 “Electrical Characteristics”.
FIGURE 22-1: 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*/RCV
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*/RCV
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.
RCV