
2002 Microchip Technology Inc.
Preliminary
DS40044A-page 61
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) 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 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
When C2INV = 0:
1
= C2 V
IN
+ > C2 V
IN
-
0
= C2 V
IN
+ < C2 V
IN
-
When C2INV = 1:
1
= C2 V
IN
+ < C2 V
IN
-
0
= C2 V
IN
+ > C2 V
IN
-
bit 6
C1OUT
: Comparator 1 Output
When C1INV = 0:
1
= C1 V
IN
+ > C1 V
IN
-
0
= C1 V
IN
+ < C1 V
IN
-
When C1INV = 1:
1
= C1 V
IN
+ < C1 V
IN
-
0
= C1 V
IN
+ > C1 V
IN
-
bit 5
C2INV
: Comparator 2 Output Inversion
1
= C2 Output inverted
0
= C2 Output not inverted
bit 4
C1INV
: Comparator 1 Output Inversion
1
= C1 Output inverted
0
= C1 Output not inverted
bit 3
CIS
: Comparator Input Switch
When CM2:CM0: = 001
Then:
1
= C1 V
IN
- connects to RA3
0
= C1 V
IN
- connects to RA0
When CM2:CM0 = 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
CM2:CM0
: Comparator Mode
Figure 10-1 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