Datasheet

 2004 Microchip Technology Inc. Preliminary DS39637A-page 257
PIC18F2480/2580/4480/4580
20.0 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 RA0 through RA5, as well as the
on-chip voltage reference (see Section 21.0
“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 20-1) selects the
comparator input and output configuration. Block
diagrams of the various comparator configurations are
shown in Figure 20-1.
REGISTER 20-1: CMCON: COMPARATOR CONTROL REGISTER
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/C1IN+
C2 V
IN+ connects to RD2/PSP2/C2IN+
0 =C1 V
IN- connects to RD1/PSP1/C1IN-
C2 V
IN- connects to RD3/PSP3/C2IN-
bit 2-0 CM2:CM0: Comparator Mode bits
Figure 20-1 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