PIC18F2221_1 Datasheet, PDF (244/402 Pages) Microchip Technology – Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology

PIC18F2221/2321/4221/4321 FAMILY
21.1 Comparator Configuration
There are eight modes of operation for the comparators,
shown in Figure 21-1. Bits CM<2:0> of the CMCON
register are used to select these modes. The TRISA reg-
ister 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 27.0
“Electrical Characteristics”.
Note:
Comparator interrupts should be disabled
during a Comparator mode change;
otherwise, a false interrupt may occur.
FIGURE 21-1:
COMPARATOR I/O OPERATING MODES
Comparators Reset
CM<2:0> = 000
Comparators Off (POR Default Value)
CM<2:0> = 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
CM<2:0> = 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
CM<2:0> = 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
CM<2:0> = 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
CM<2:0> = 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
CM<2:0> = 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
CM<2:0> = 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.
DS39689F-page 244
© 2009 Microchip Technology Inc.