PIC16F87 Datasheet, PDF (124/214 Pages) Microchip Technology – 18/20/28-Pin Enhanced FLASH Microcontrollers with nanoWatt Technology

PIC16F87/88
13.1 Comparator Configuration
There are eight modes of operation for the compara-
tors. The CMCON register is used to select these
modes. Figure 13-1 shows the eight possible 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 18.0 “Electrical Characteristics”.
Note:
Comparator interrupts should be disabled
during a Comparator mode change.
Otherwise, a false interrupt may occur.
FIGURE 13-1:
COMPARATOR I/O OPERATING MODES
Comparators Reset
CM2:CM0 = 000
Comparators Off (POR Default Value)
CM2:CM0 = 111
RA0/AN0 ^A
RA3/AN3 ^A
VIN-
VIN+ ^C1
Off (Read as ‘0’)
RA0/AN0 ^D
RA3/AN3 ^D
VIN-
VIN+ ^C1
Off (Read as ‘0’)
RA1/AN1 ^A
RA2/AN2 ^A
VIN-
VIN+ ^C2
Two Independent Comparators
CM2:CM0 = 100
RA0/AN0 ^A
RA3/AN3 ^A
VIN-
VIN+ ^C1
RA1/AN1 ^A
RA2/AN2 ^A
VIN-
VIN+ ^C2
Off (Read as ‘0’)
C1OUT
C2OUT
Two Common Reference Comparators
CM2:CM0 = 011
RA0/AN0 ^A
RA3/AN3 ^D
VIN-
VIN+ ^C1
C1OUT
RA1/AN1 ^D
RA2/AN2 ^D
VIN-
VIN+ ^C2
Off (Read as ‘0’)
Four Inputs Multiplexed to Two Comparators
CM2:CM0 = 010
RA0/AN0 ^A
RA3/AN3 ^A
CIS = 0
CIS = 1
VIN-
VIN+ ^C1
RA1/AN1 ^A
RA2/AN2 ^A
CIS = 0
CIS = 1
VIN-
VIN+ ^C2
C1OUT
C2OUT
From VREF Module
Two Common Reference Comparators with Outputs
CM2:CM0 = 110
RA0/AN0 ^A
RA3/AN3 ^D
VIN-
VIN+ ^C1
C1OUT
RA1/AN1 ^A
RA2/AN2 ^A
VIN-
VIN+ ^C2
C2OUT
One Independent Comparator
CM2:CM0 = 101
RA0/AN0 ^D
RA3/AN3 ^D
VIN-
VIN+ ^C1
Off (Read as ‘0’)
RA1/AN1 ^A
RA2/AN2 ^A
VIN-
VIN+ ^C2
C2OUT
A = Analog Input, port reads zeros always.
D = Digital Input.
CIS (CMCON<3>) is the Comparator Input Switch.
RA1/AN1 ^A
RA2/AN2 ^A
VIN-
VIN+ ^C2
C2OUT
RA4/T0CKI
Three Inputs Multiplexed to Two Comparators
CM2:CM0 = 001
RA0/AN0 ^A
RA3/AN3 ^A
CIS = 0
CIS = 1
VIN-
VIN+ ^C1
C1OUT
RA1/AN1 ^A
RA2/AN2 ^A
VIN-
VIN+ ^C2
C2OUT
DS30487B-page 122
Preliminary
 2003 Microchip Technology Inc.