Datasheet

© 2006 Microchip Technology Inc. DS41159E-page 249
PIC18FXX8
21.0 COMPARATOR MODULE
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
Note: The analog comparators are only
available on the PIC18F448 and
PIC18F458.
R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
C2OUT C1OUT C2INV C1INV CIS CM2 CM1 CM0
bit 7 bit 0
bit 7 C2OUT: Comparator 2 Output bit
When C2INV =
0:
1 = C2 VIN+ > C2 VIN-
0 = C2 V
IN+ < C2 VIN-
When C2INV =
1:
1 = C2 VIN+ < C2 VIN-
0 = C2 V
IN+ > C2 VIN-
bit 6 C1OUT: Comparator 1 Output bit
When C1INV = 0:
1 = C1 VIN+ > C1 VIN-
0 = C1 V
IN+ < C1 VIN-
When C1INV =
1:
1 = C1 VIN+ < C1 VIN-
0 = C1 V
IN+ > C1 VIN-
bit 5 C2INV: Comparator 2 Output Inversion bit
1 = C2 output inverted
0 = C2 output not inverted
bit 4 C1INV: Comparator 1 Output Inversion bit
1 = C1 output inverted
0 = C1 output not inverted
bit 3 CIS: Comparator Input Switch bit
When CM2:CM0 =
110:
1 =C1 VIN- connects to RD0/PSP0
C2 V
IN- connects to RD2/PSP2
0 =C1 V
IN- connects to RD1/PSP1
C2 V
IN- connects to RD3/PSP3
bit 2-0 CM2:CM0: Comparator Mode bits
Figure 21-1 shows the Comparator modes and CM2:CM0 bit settings.
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown