PIC24FJ128GA310 datasheet(172/406 Pages) MICROCHIP

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PIC24FJ128GA310 FAMILY

DS39996F-page 172

 2010-2011 Microchip Technology Inc.

11.3

Input Change Notification

The input change notification function of the I/O ports

allows the PIC24FJ128GA310 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

82 external inputs that may be selected (enabled) for

generating an interrupt request on a Change-of-State.

Registers, CNEN1 through CNEN6, contain the inter-

rupt 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 has both a weak pull-up and a weak

pull-down connected to it. The pull-ups act as a current

source that is connected to the pin, while the

pull-downs act as a current sink that is connected to the

pin. These eliminate the need for external resistors

when push button or keypad devices are connected.

The pull-ups and pull-downs are separately enabled

using the CNPU1 through CNPU6 registers (for

pull-ups) and the CNPD1 through CNPD6 registers (for

pull-downs). Each CN pin has individual control bits for

its pull-up and pull-down. Setting a control bit enables

the weak pull-up or pull-down for the corresponding

pin.

When the internal pull-up is selected, the pin pulls up to

VDD – 1.1V (typical). When the internal pull-down is

selected, the pin pulls down to VSS.

EXAMPLE 11-1:

PORT WRITE/READ IN ASSEMBLY

EXAMPLE 11-2:

PORT WRITE/READ IN ‘C’

Note:

Pull-ups on change notification pins

should always be disabled whenever the

port pin is configured as a digital output.

MOV

0xFF00, W0

; Configure PORTB<15:8> as inputs

MOV

W0, TRISB

; and PORTB<7:0> as outputs

NOP

; Delay 1 cycle

BTSS

PORTB, #13

; Next Instruction

TRISB = 0xFF00;

// Configure PORTB<15:8> as inputs and PORTB<7:0> as outputs

Nop();

// Delay 1 cycle

If (PORTBbits.RB13){ };

// Next Instruction

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