Datasheet

PIC18F2682/2685/4682/4685
DS39761C-page 260 © 2009 Microchip Technology Inc.
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 27.0 “Electrical Characteristics”.
FIGURE 20-1: COMPARATOR I/O OPERATING MODES
Note: Comparator interrupts should be disabled
during a Comparator mode change;
otherwise, a false interrupt may occur.
C1
VIN-
V
IN+
Off
Comparators Reset (POR Default Value)
A
A
CM2:CM0 = 000
C2
VIN-
V
IN+
Off
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
One Independent Comparator with Output
D
D
CM2:CM0 = 001
C1
VIN-
V
IN+
C1OUT
A
A
C1
VIN-
V
IN+
Off
Comparators Off
D
D
CM2:CM0 = 111
C2
VIN-
V
IN+
Off
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
* Setting the TRISA<5:4> bits will disable the comparator outputs by configuring the pins as inputs.
(Read as ‘0’)
(Read as ‘0’)
(Read as ‘0’)
(Read as ‘0’)
(Read as ‘0’)
RD1/PSP1/C1IN-
RD0/PSP0/C1IN+
RD3/PSP3/C2IN-
RD2/PSP2/C2IN+
RD1/PSP1/C1IN-
RD0/PSP0/C1IN+
RD3/PSP3/C2IN-
RD2/PSP2/C2IN+
RD1/PSP1/C1IN-
RD0/PSP0/C1IN+
RD3/PSP3/C2IN-
RD2/PSP2/C2IN+
RD1/PSP1/C1IN-
RD0/PSP0/C1IN+
RD3/PSP3/C2IN-
RD2/PSP2/C2IN+
RD1/PSP1/C1IN-
RD0/PSP0/C1IN+
RD3/PSP3/C2IN-
RD2/PSP2/C2IN+
RD1/PSP1/C1IN-
RD0/PSP0/C1IN+
RD3/PSP3/C2IN-
RD2/PSP2/C2IN+
RD1/PSP1/
RD0/PSP0/
RD3/PSP3/
RD2/PSP2/
C2IN-
C2IN+
C1IN+
C1IN-
RE1/WR
/AN6/C1OUT*
RE1/WR
/AN6/C1OUT*
RE2/CS
/AN7/C2OUT*
RD1/PSP1/C1IN-
RD0/PSP0/C1IN+
RD3/PSP3/C2IN-
RD2/PSP2/C2IN+
RE1/WR
/AN6/C1OUT*
RE2/CS
/AN7/C2OUT*