Datasheet

© 2007 Microchip Technology Inc. DS39629C-page 241
PIC18F6390/6490/8390/8490
19.0 COMPARATOR MODULE
The analog comparator module contains two
comparators that can be configured in a variety of
ways. The inputs can be selected from the analog
inputs multiplexed with pins RF3 through RF6, as well
as the on-chip voltage reference (see Section 20.0
“Comparator Voltage Reference Module”). The digi-
tal 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
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
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 RF5/AN10
C2 V
IN- connects to RF3/AN8
0 =C1 V
IN- connects to RF6/AN11
C2 V
IN- connects to RF4/AN9
bit 2-0 CM2:CM0: Comparator Mode bits
Figure 19-1 shows the Comparator modes and the CM2:CM0 bit settings.