PIC18F4321 Datasheet, PDF (240/396 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology

PIC18F4321 FAMILY
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”.
Note:
Comparator interrupts should be disabled
during a Comparator mode change;
otherwise, a false interrupt may occur.
FIGURE 20-1:
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*
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
A
RA0/AN0
RA3/AN3/ ^A
VREF+
VIN-
VIN+ ^C1
C1OUT
RA4/T0CKI/C1OUT*
RA1/AN1 ^A
VIN-
RA2/AN2/ _D
VREF-/CVREF
VIN+ ^C2
RA5/AN4/SS/HLVDIN/C2OUT*
C2OUT
One Independent Comparator with Output
CM2:CM0 = 001
RA0/AN0 ^A
RA3/AN3/ A
VREF+
VIN-
VIN+ ^C1
C1OUT
RA4/T0CKI/C1OUT*
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.
DS39689E-page 238
Preliminary
© 2007 Microchip Technology Inc.