Datasheet

 2011 Microchip Technology Inc. DS39932D-page 367
PIC18F46J11 FAMILY
22.6 Comparator Interrupts
The comparator interrupt flag is set whenever any of
the following occurs:
- Low-to-high transition of the comparator
output
- High-to-low transition of the comparator
output
- Any change in the comparator output
The comparator interrupt selection is done by the
EVPOL<1:0> bits in the CMxCON register
(CMxCON<4:3>).
In order to provide maximum flexibility, the output of the
comparator may be inverted using the CPOL bit in the
CMxCON register (CMxCON<5>). This is functionally
identical to reversing the inverting and non-inverting
inputs of the comparator for a particular mode.
An interrupt is generated on the low-to-high or high-to-
low transition of the comparator output. This mode of
interrupt generation is dependent on EVPOL<1:0> in
the CMxCON register. When EVPOL<1:0> = 01 or 10,
the interrupt is generated on a low-to-high or high-to-
low transition of the comparator output. Once the
interrupt is generated, it is required to clear the interrupt
flag by software.
When EVPOL<1:0> = 11, the comparator interrupt flag
is set whenever there is a change in the output value of
either comparator. Software will need to maintain
information about the status of the output bits, as read
from CMSTAT<1:0>, to determine the actual change
that occurred. The CMxIF bits (PIR2<6:5>) are the
Comparator Interrupt Flags. The CMxIF bits must be
reset by clearing them. Since it is also possible to write
a ‘1’ to this register, a simulated interrupt may be
initiated.
Table 22-2 provides the interrupt generation
corresponding to comparator input voltages and
EVPOL bit settings.
Both the CMxIE bits (PIE2<6:5>) and the PEIE bit
(INTCON<6>) must be set to enable the interrupt. In
addition, the GIE bit (INTCON<7>) must also be set.
If any of these bits are clear, the interrupt is not
enabled, though the CMxIF bits will still be set if an
interrupt condition occurs.
Figure 22-1 provides a simplified diagram of the
interrupt section.
TABLE 22-2: COMPARATOR INTERRUPT GENERATION
CPOL EVPOL<1:0>
Comparator
Input Change
COUTx Transition
Interrupt
Generated
0
00
V
IN+ > VIN- Low-to-High No
VIN+ < VIN-High-to-Low No
01
V
IN+ > VIN- Low-to-High Yes
VIN+ < VIN-High-to-Low No
10
VIN+ > VIN- Low-to-High No
V
IN+ < VIN-High-to-Low Yes
11
VIN+ > VIN- Low-to-High Yes
V
IN+ < VIN-High-to-Low Yes
1
00
V
IN+ > VIN-High-to-Low No
VIN+ < VIN- Low-to-High No
01
V
IN+ > VIN-High-to-Low No
V
IN+ < VIN- Low-to-High Yes
10
VIN+ > VIN-High-to-Low Yes
V
IN+ < VIN- Low-to-High No
11
V
IN+ > VIN-High-to-Low Yes
VIN+ < VIN- Low-to-High Yes