Datasheet

© 2009 Microchip Technology Inc. DS40044G-page 63
PIC16F627A/628A/648A
10.0 COMPARATOR MODULE
The comparator module contains two analog
comparators. The inputs to the comparators are
multiplexed with the RA0 through RA3 pins. The on-chip
Voltage Reference (Section 11.0 “Voltage Reference
Module”) can also be an input to the comparators.
The CMCON register, shown in Register 10-1, controls
the comparator input and output multiplexers. A block
diagram of the comparator is shown in Figure 10-1.
REGISTER 10-1: CMCON – COMPARATOR CONFIGURATION REGISTER (ADDRESS: 01Fh)
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 CM<2:0>: =
001
Then:
1 = C1 V
IN- connects to RA3
0 = C1 V
IN- connects to RA0
When CM<2:0> =
010
Then:
1 = C1 V
IN- connects to RA3
C2 V
IN- connects to RA2
0 = C1 V
IN- connects to RA0
C2 V
IN- connects to RA1
bit 2-0 CM<2:0>: Comparator Mode bits
Figure 10-1 shows the comparator modes and CM<2:0> 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