PIC18FXX8 Datasheet, PDF (251/402 Pages) Microchip Technology – 28/40-Pin High-Performance, Enhanced Flash Microcontrollers with CAN Module

PIC18FXX8
21.0 COMPARATOR MODULE
Note:
The analog comparators are only
available on the PIC18F448 and
PIC18F458.
The comparator module contains two analog com-
parators. The inputs to the comparators are
multiplexed with the RD0 through RD3 pins. The on-chip
voltage reference (Section 22.0 “Comparator Voltage
Reference Module”) can also be an input to the
comparators.
The CMCON register, shown in Register 21-1, controls
the comparator input and output multiplexers. A block
diagram of the comparator is shown in Figure 21-1.
REGISTER 21-1:
CMCON: COMPARATOR CONTROL REGISTER
R-0
R-0
R/W-0 R/W-0 R/W-0
C2OUT C1OUT C2INV C1INV
CIS
bit 7
R/W-0
CM2
R/W-0
CM1
R/W-0
CM0
bit 0
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2-0
C2OUT: Comparator 2 Output bit
When C2INV = 0:
1 = C2 VIN+ > C2 VIN-
0 = C2 VIN+ < C2 VIN-
When C2INV = 1:
1 = C2 VIN+ < C2 VIN-
0 = C2 VIN+ > C2 VIN-
C1OUT: Comparator 1 Output bit
When C1INV = 0:
1 = C1 VIN+ > C1 VIN-
0 = C1 VIN+ < C1 VIN-
When C1INV = 1:
1 = C1 VIN+ < C1 VIN-
0 = C1 VIN+ > C1 VIN-
C2INV: Comparator 2 Output Inversion bit
1 = C2 output inverted
0 = C2 output not inverted
C1INV: Comparator 1 Output Inversion bit
1 = C1 output inverted
0 = C1 output not inverted
CIS: Comparator Input Switch bit
When CM2:CM0 = 110:
1 = C1 VIN- connects to RD0/PSP0
C2 VIN- connects to RD2/PSP2
0 = C1 VIN- connects to RD1/PSP1
C2 VIN- connects to RD3/PSP3
CM2:CM0: Comparator Mode bits
Figure 21-1 shows the Comparator modes and CM2:CM0 bit settings.
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
 2004 Microchip Technology Inc.
DS41159D-page 249