Datasheet

© 2009 Microchip Technology Inc. DS39636D-page 223
PIC18F2X1X/4X1X
19.0 COMPARATOR MODULE
The analog comparator module contains two compara-
tors that can be configured in a variety of ways. The
inputs can be selected from the analog inputs multiplexed
with pins RA0 through RA5, as well as the on-chip volt-
age reference (see Section 20.0 “Comparator Voltage
Reference Module”). The digital outputs (normal or
inverted) are available at the pin level and can also be
read through the control register.
The CMCON register (Register 19-1) selects the
comparator input and output configuration. Block
diagrams of the various comparator configurations are
shown in Figure 19-1.
REGISTER 19-1: CMCON: COMPARATOR CONTROL REGISTER
R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-1 R/W-1 R/W-1
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 RA3/AN3/VREF+
C2 V
IN+ connects to RA2/AN2/VREF-/CVREF
0 =C1 VIN- connects to RA0/AN0
C2 V
IN- connects to RA1/AN1
bit 2-0 CM2:CM0: Comparator Mode bits
Figure 19-1 shows the Comparator modes and the 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