PIC18F2455_09 Datasheet, PDF (278/438 Pages) Microchip Technology – 28/40/44-Pin,High-Performance,Enhanced Flash,USB Microcontrollers with nanoWatt Technology

PIC18F2455/2550/4455/4550
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”.
Note:
Comparator interrupts should be disabled
during a Comparator mode change.
Otherwise, a false interrupt may occur.
FIGURE 22-1:
COMPARATOR I/O OPERATING MODES
Comparators Reset
CM2:CM0 = 000
Comparators Off (POR Default Value)
CM2:CM0 = 111
RA0/AN0 ^A
RA3/AN3/ ^A
VREF+
VIN-
VIN+ ^C1
Off (Read as ‘0’)
RA0/AN0 ^D
RA3/AN3/ D
VREF+
VIN-
VIN+ ^C1
Off (Read as ‘0’)
RA1/AN1 ^A
RA2/AN2/ ^A
VREF-/CVREF
VIN-
VIN+ ^C2
Two Independent Comparators
CM2:CM0 = 010
RA0/AN0 ^A
VIN-
RA3/AN3/ ^A
VREF+
VIN+ ^C1
RA1/AN1 ^A
RA2/AN2/ ^A
VREF-/CVREF
VIN-
VIN+ ^C2
Off (Read as ‘0’)
C1OUT
C2OUT
RA1/AN1 ^D
RA2/AN2/ D
VREF-/CVREF
VIN-
VIN+ ^C2
Off (Read as ‘0’)
Two Independent Comparators with Outputs
CM2:CM0 = 011
RA0/AN0 ^A
RA3/AN3/ A
VREF+
VIN-
VIN+ ^C1
C1OUT
RA4/T0CKI/C1OUT*/RCV
RA1/AN1 ^A
RA2/AN2/ A
VREF-/CVREF
VIN-
VIN+ ^C2
RA5/AN4/SS/HLVDIN/C2OUT*
C2OUT
Two Common Reference Comparators
CM2:CM0 = 100
RA0/AN0 ^A
RA3/AN3/ ^A
VREF+
VIN-
VIN+ ^C1
C1OUT
RA1/AN1 ^A
RA2/AN2/ ^D
VREF-/CVREF
VIN-
VIN+ ^C2
C2OUT
Two Common Reference Comparators with Outputs
CM2:CM0 = 101
RA0/AN0
RA3/AN3/
VREF+
A
VIN-
A
VIN+ ^C1
C1OUT
RA4/T0CKI/C1OUT*/
RCV
RA1/AN1
A
RA2/AN2/
D
VREF-/CVREF
VIN-
VIN+ ^C2
C2OUT
RA5/AN4/SS/HLVDIN/C2OUT*
One Independent Comparator with Output
CM2:CM0 = 001
RA0/AN0 ^A
RA3/AN3/ A
VREF+
VIN-
VIN+ ^C1
C1OUT
RA4/T0CKI/C1OUT*/RCV
RA1/AN1 ^D
RA2/AN2/ D
VREF-/CVREF
VIN-
VIN+ ^C2
Off (Read as ‘0’)
Four Inputs Multiplexed to Two Comparators
CM2:CM0 = 110
RA0/AN0 ^A
RA3/AN3/ ^A
VREF+
CIS = 0
CIS = 1
VIN-
VIN+ ^C1
RA1/AN1 ^A
RA2/AN2/ ^A
VREF-/CVREF
CIS = 0
CIS = 1
VIN-
VIN+ ^C2
C1OUT
C2OUT
CVREF _{From VREF Module}
A = Analog Input, port reads zeros always
D = Digital Input
CIS (CMCON<3>) is the Comparator Input Switch
* Setting the TRISA<5:4> bits will disable the comparator outputs by configuring the pins as inputs.
DS39632E-page 276
© 2009 Microchip Technology Inc.