PIC24FJ64GA006-I Datasheet, PDF (109/258 Pages) Microchip Technology – 64/80/100-Pin, General Purpose, 16-Bit Flash Microcontrollers

PIC24FJ128GA010 FAMILY
10.3 Input Change Notification
The input change notification function of the I/O ports
allows the PIC24FJ128GA010 family of devices to gen-
erate interrupt requests to the processor in response to
a Change-of-State (COS) on selected input pins. This
feature is capable of detecting input Change-of-States,
even in Sleep mode, when the clocks are disabled.
Depending on the device pin count, there are up to
22 external signals (CN0 through CN21) that may be
selected (enabled) for generating an interrupt request
on a Change-of-State.
There are four control registers associated with the CN
module. The CNEN1 and CNEN2 registers contain the
interrupt enable control bits for each of the CN input
pins. Setting any of these bits enables a CN interrupt
for the corresponding pins.
Each CN pin also has a weak pull-up connected to it.
The pull-ups act as a current source that is connected
to the pin and eliminate the need for external resistors
when push button or keypad devices are connected.
The pull-ups are enabled separately using the CNPU1
and CNPU2 registers, which contain the control bits for
each of the CN pins. Setting any of the control bits
enables the weak pull-ups for the corresponding pins.
When the internal pull-up is selected, the pin pulls up to
VDD – 0.7V (typical). Make sure that there is no external
pull-up source when the internal pull-ups are enabled, as
the voltage difference can cause a current path.
Note:
Pull-ups on Change Notification (CN) pins
should always be disabled whenever the
port pin is configured as a digital output.
 2005-2012 Microchip Technology Inc.
DS39747F-page 109