Datasheet

 2001-2013 Microchip Technology Inc. DS39582C-page 135
PIC16F87XA
12.0 COMPARATOR MODULE
The comparator module contains two analog compara-
tors. The inputs to the comparators are multiplexed
with I/O port pins RA0 through RA3, while the outputs
are multiplexed to pins RA4 and RA5. The on-chip volt-
age reference (Section 13.0 “Comparator Voltage
Reference Module”) can also be an input to the
comparators.
The CMCON register (Register 12-1) controls the com-
parator input and output multiplexers. A block diagram
of the various comparator configurations is shown in
Figure 12-1.
REGISTER 12-1: CMCON 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
C2 V
IN- connects to RA2/AN2
0 =C1 V
IN- connects to RA0/AN0
C2 V
IN- connects to RA1/AN1
bit 2 CM2:CM0: Comparator Mode bits
Figure 12-1 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