PIC24F16KL402 Datasheet, PDF (114/260 Pages) Microchip Technology – Low-Power, Low-Cost, General Purpose 16-Bit Flash Microcontrollers with nanoWatt XLP Technology

PIC24F16KL402 FAMILY
11.3 Input Change Notification
The input change notification function of the I/O ports
allows the PIC24F16KL402 family of devices to gener-
ate 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
23 external signals that may be selected (enabled) for
generating an interrupt request on a Change-of-State.
There are six 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/pull-down
connected to it. The pull-ups act as a current source
that is connected to the pin. The pull-downs act as a
current sink to eliminate the need for external resistors
when push button or keypad devices are connected.
On any pin, only the pull-up resistor or the pull-down
resistor should be enabled, but not both of them. If the
push button or the keypad is connected to VDD, enable
the pull-down, or if they are connected to VSS, enable
the pull-up resistors. The pull-ups are enabled sepa-
rately 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. The pull-downs are
enabled separately, using the CNPD1 and CNPD2
registers, which contain the control bits for each of the
CN pins. Setting any of the control bits enables the
weak pull-downs for the corresponding pins.
When the internal pull-up is selected, the pin uses VDD
as the pull-up source voltage. When the internal
pull-down is selected, the pins are pulled down to VSS
by an internal resistor. Make sure that there is no exter-
nal pull-up source/pull-down sink when the internal
pull-ups/pull-downs are enabled.
Note:
Pull-ups and pull-downs on change notifi-
cation pins should always be disabled
whenever the port pin is configured as a
digital output.
EXAMPLE 11-1: PORT WRITE/READ EXAMPLE (ASSEMBLY LANGUAGE)
MOV
MOV
MOV
MOV
NOP
BTSS
#0xFF00, W0
W0, TRISB
#0x00FF, W0
W0, ANSB
PORTB, #13
; Configure PORTB<15:8> as inputs and PORTB<7:0> as outputs
; Enable PORTB<15:8> digital input buffers
; Delay 1 cycle
; Next Instruction
EXAMPLE 11-2: PORT WRITE/READ EXAMPLE (C LANGUAGE)
TRISB = 0xFF00;
ANSB = 0x00FF;
NOP();
if(PORTBbits.RB13 == 1)
{
}
// Configure PORTB<15:8> as inputs and PORTB<7:0> as outputs
// Enable PORTB<15:8> digital input buffers
// Delay 1 cycle
// execute following code if PORTB pin 13 is set.
DS31037B-page 114
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