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Interrupt Structure
The pin must also be setup as an input by setting the
corresponding PAC.6 and PAC.7 bits in the port control
register. When the interrupt is enabled, the stack is not
full and the correct transition type appears on the
external interrupt pin, a subroutine call to the external
interrupt vector at location 04H or 08H, will take place.
When the interrupt is serviced, the external interrupt
request flags, EIF0 or EIF1, will be automatically reset
and the EMI bit will be automatically cleared to disable
other interrupts. Note that any pull-high resistor
selections on this pin will remain valid even if the pin is
used as an external interrupt input.
rupts due to adverse noise or spikes on the external in-
terrupt input signal. As this internal filter circuit will
consume a limited amount of power, a configuration op-
tion is provided to switch off the filter function, an option
which may be beneficial in power sensitive applications,
but in which the integrity of the input signal is high. Care
must be taken when using the filter on/off configuration
option as it will be applied not only to both the external
interrupt pins but also to the Timer/Event Counter exter-
nal input pins. Individual external interrupt or
Timer/Event Counter pins cannot be selected to have a
filter on/off function.
The INTEDGE register is used to select the type of active
edge that will trigger the external interrupt. A choice of ei-
ther rising and falling edge types can be chosen along
with an option to allow both edge types to trigger an exter-
nal interrupt. Note that the INTEDGE register can also be
used to disable the external interrupt function.
External Peripheral Interrupt
The External Peripheral Interrupt operates in a similar
way to the external interrupt and is contained within
Multi-function Interrupt 1.
For an external peripheral interrupt to occur, the global
interrupt enable bit, EMI, external peripheral interrupt
enable bit, EPI, and Multi-function Interrupt 1 enable bit,
The external interrupt pins are connected to an internal
filter to reduce the possibility of unwanted external inter-
Rev. 1.20
54
February 25, 2011
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
