Microchip Technology AC244045 Data Sheet

 2010-2012 Microchip Technology Inc.

DS41440C-page 139

The PORTA pins can be configured to operate as
Interrupt-on-Change (IOC) pins. On the PIC16(L)F1829
devices, the PORTB pins can also be configured to
operate as 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

 is a block diagram of the IOC 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.

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.

The IOCAFx and IOCBFx bits located in the IOCAF and
IOCBF registers, respectively, 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 and IOCBFx bits.

The individual status flags, (IOCAFx and 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.

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
register will be updated prior to the first instruction
executed out of Sleep. 

MOVLW

0xff

XORWF

IOCAF, W

ANDWF

IOCAF, F