PIC16LF18854 Datasheet, PDF (258/668 Pages) Microchip Technology – C Compiler Optimized RISC Architecture

PIC16(L)F18856/76
15.0 INTERRUPT-ON-CHANGE
All pins on all ports (except PORTD on PIC16F18875
devices) 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 pin, or combination
of 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 15-1 is a block diagram of the IOC module.
15.1 Enabling the Module
To allow individual pins to generate an interrupt, the
IOCIE bit of the PIE0 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.
15.2 Individual Pin Configuration
For each 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 the associated bits in
both of the IOCxP and IOCxN registers.
15.3 Interrupt Flags
The bits located in the IOCxF registers are status flags
that correspond to the interrupt-on-change pins of each
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 PIR0 register reflects the status of
all IOCxF bits.
15.4 Clearing Interrupt Flags
The individual status flags, (IOCxF register 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 15-1:
CLEARING INTERRUPT
FLAGS
(PORTA EXAMPLE)
MOVLW 0xff
XORWF IOCAF, W
ANDWF IOCAF, F
15.5 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 affected
IOCxF register will be updated prior to the first instruction
executed out of Sleep.
DS40001824A-page 258
Preliminary
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