INTEDG datasheet(153/478 Pages) MICROCHIP

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DS41414D-page 153

PIC16(L)F1946/47

13.0 INTERRUPT-ON-CHANGE

The PORTB pins can be configured to operate as

Interrupt-On-Change (IOC) pins. An interrupt can be

generated by detecting a signal that has either a rising

edge or a falling edge. Any individual PORTB pin, or

combination of PORTB pins, can be configured to

generate an interrupt. The interrupt-on-change module

has the following features:

• Interrupt-on-change enable (Master Switch)

• Individual pin configuration

• Rising and falling edge detection

• Individual pin interrupt flags

Figure 13-1 is a block diagram of the IOC module.

13.1

Enabling the Module

To allow individual PORTB pins to generate an interrupt,

the IOCIE bit of the INTCON register must be set. If the

IOCIE bit is disabled, the edge detection on the pin will

still occur, but an interrupt will not be generated.

13.2

Individual Pin Configuration

For each PORTB pin, a rising edge detector and a falling

edge detector are present. To enable a pin to detect a

rising edge, the associated IOCBPx bit of the IOCBP

the associated IOCBNx bit of the IOCBN register is set.

A pin can be configured to detect rising and falling

edges simultaneously by setting both the IOCBPx bit

and the IOCBNx bit of the IOCBP and IOCBN registers,

respectively.

13.3

Interrupt Flags

The IOCBFx bits located in the IOCBF register are

status flags that correspond to the Interrupt-on-change

pins of PORTB. If an expected edge is detected on an

appropriately enabled pin, then the status flag for that pin

will be set, and an interrupt will be generated if the IOCIE

bit is set. The IOCIF bit of the INTCON register reflects

the status of all IOCBFx bits.

13.4

Clearing Interrupt Flags

The individual status flags, (IOCBFx bits), can be

cleared by resetting them to zero. If another edge is

detected during this clearing operation, the associated

status flag will be set at the end of the sequence,

regardless of the value actually being written.

In order to ensure that no detected edge is lost while

clearing flags, only AND operations masking out known

changed bits should be performed. The following

sequence is an example of what should be performed.

EXAMPLE 13-1:

CLEARING INTERRUPT

FLAGS

(PORTA EXAMPLE)

13.5

Operation in Sleep

The interrupt-on-change interrupt sequence will wake

the device from Sleep mode, if the IOCIE bit is set.

If an edge is detected while in Sleep mode, the IOCBF

executed out of Sleep.

MOVLW

0xff

XORWF

IOCAF, W

ANDWF

IOCAF, F

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