Datasheet

PIC12F635/PIC16F636/639
DS41232D-page 76 © 2007 Microchip Technology Inc.
7.4 Comparator Control
The CMCON0 register (Register 7-1) provides access
to the following comparator features:
• Mode selection
• Output state
• Output polarity
• Input switch
7.4.1 COMPARATOR OUTPUT STATE
Each comparator state can always be read internally
via the CxOUT bit of the CMCON0 register. The com-
parator state may also be directed to the CxOUT pin in
the following modes:
PIC12F635
• CM<2:0> = 001
• CM<2:0> = 011
• CM<2:0> = 101
PIC16F636/639
• CM<2:0> = 110
When one of the above modes is selected, the
associated TRIS bit of the CxOUT pin must be cleared.
7.4.2 COMPARATOR OUTPUT POLARITY
Inverting the output of a comparator is functionally
equivalent to swapping the comparator inputs. The
polarity of a comparator output can be inverted by set-
ting the C
XINV bit of the CMCON0 register. Clearing
C
XINV results in a non-inverted output. A complete
table showing the output state versus input conditions
and the polarity bit is shown in Table 7-1.
TABLE 7-1: OUTPUT STATE VS. INPUT
CONDITIONS
7.4.3 COMPARATOR INPUT SWITCH
The inverting input of the comparators may be switched
between two analog pins in the following modes:
PIC12F635
•CM<2:0> = 101
•CM<2:0> = 110
PIC16F636/639
•CM<2:0> = 001 (Comparator C1 only)
•CM<2:0> = 010 (Comparators C1 and C2)
In the above modes, both pins remain in Analog mode
regardless of which pin is selected as the input. The
CIS bit of the CMCON0 register controls the comparator
input switch.
Input Conditions CxINV CxOUT
V
IN- > VIN+ 00
VIN- < VIN+ 01
V
IN- > VIN+ 11
VIN- < VIN+ 10
Note: CxOUT refers to both the register bit and
output pin.