PIC16C620 Microchip Technology, PIC16C620 Datasheet - Page 41

• Manufacturer Part Number: PIC16C620
• Description: EPROM-Based 8-Bit CMOS Microcontroller
• Manufacturer: Microchip Technology

7.6
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 CMCON<7:6>, to
determine the actual change that has occurred. The
CMIF bit, PIR1<6>, is the comparator interrupt flag.
The CMIF bit must be reset by clearing ‘0’. Since it is
also possible to write a '1' to this register, a simulated
interrupt may be initiated.
The
(INTCON<6>) must be set to enable the interrupt. In
addition, the GIE bit must also be set. If any of these
bits are clear, the interrupt is not enabled, though the
CMIF bit will still be set if an interrupt condition occurs.
The user, in the interrupt service routine, can clear the
interrupt in the following manner:
7.7
When a comparator is active and the device is placed
in SLEEP mode, the comparator remains active and
the interrupt is functional if enabled. This interrupt will
FIGURE 7-5:
a)
b)
A mismatch condition will continue to set flag bit CMIF.
Reading CMCON will end the mismatch condition, and
allow flag bit CMIF to be cleared.
1998 Microchip Technology Inc.
Note:
Any read or write of CMCON. This will end the
mismatch condition.
Clear flag bit CMIF.
CMIE
Comparator Interrupts
Comparator Operation During SLEEP
If a change in the CMCON register
(C1OUT or C2OUT) should occur when a
read operation is being executed (start of
the Q2 cycle), then the CMIF (PIR1<6>)
interrupt flag may not get set.
bit
VA
Legend
R
ANALOG INPUT MODEL
S
(PIE1<6>)
< 10K
A
IN
C
V
I
R
R
VA
LEAKAGE
T
PIN
IC
S
and
C
5 pF
PIN
the
= Input Capacitance
= Threshold Voltage
= Leakage Current At The Pin Due To Various Junctions
= Interconnect Resistance
= Source Impedance
= Analog Voltage
PEIE
Preliminary
bit
V
DD
V
V
T
T
= 0.6V
= 0.6V
wake up the device from SLEEP mode when enabled.
While the comparator is powered-up, higher sleep
currents than shown in the power down current
specification will occur. Each comparator that is
operational will consume additional current as shown in
the comparator specifications. To minimize power
consumption while in SLEEP mode, turn off the
comparators, CM<2:0> = 111, before entering sleep. If
the device wakes-up from sleep, the contents of the
CMCON register are not affected.
7.8
A device reset forces the CMCON register to its reset
state. This forces the comparator module to be in the
comparator
ensures that all potential inputs are analog inputs.
Device current is minimized when analog inputs are
present at reset time. The comparators will be
powered-down during the reset interval.
7.9
A simplified circuit for an analog input is shown in
Figure 7-5. Since the analog pins are connected to a
digital output, they have reverse biased diodes to V
and V
V
range by more than 0.6V in either direction, one of the
diodes is forward biased and a latch-up may occur. A
maximum
recommended for the analog sources. Any external
component connected to an analog input pin, such as
a capacitor or a Zener diode, should have very little
leakage current.
SS
and V
SS
. The analog input therefore, must be between
Effects of a RESET
Analog Input Connection
Considerations
I
V
LEAKAGE
DD
500 nA
SS
source
. If the input voltage deviates from this
reset
R
IC
mode,
impedance
PIC16C62X
CM2:CM0 = 000. This
DS30235G-page 41
of
10 k
DD
is