PIC12LF1501 datasheet(104/352 Pages) MICROCHIP

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PIC16(L)F1503

DS40001607D-page 104

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12.0

INTERRUPT-ON-CHANGE

The PORTA 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 port pin, or

combination of port 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 12-1 is a block diagram of the IOC module.

12.1

Enabling the Module

To allow individual port 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.

12.2

Individual Pin Configuration

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

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

rising edge, the associated bit of the IOCxP register is

set. To enable a pin to detect a falling edge, the

associated bit of the IOCxN register is set.

A pin can be configured to detect rising and falling

edges simultaneously by setting both associated bits of

the IOCxP and IOCxN registers, respectively.

12.3

Interrupt Flags

The IOCAFx bits located in the IOCAF register are

status flags that correspond to the interrupt-on-change

pins of the associated port. 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 IOCAFx bits.

12.4

Clearing Interrupt Flags

The individual status flags, (IOCAFx 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 12-1:

CLEARING INTERRUPT

FLAGS

(PORTA EXAMPLE)

12.5

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 IOCxF

executed out of Sleep.

MOVLW

0xff

XORWF

IOCAF, W

ANDWF

IOCAF, F

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