Microchip Technology DM160214 Data Sheet

 2010-2012 Microchip Technology Inc.

DS41414D-page 91

Some interrupts can be used to wake from Sleep. To
wake from Sleep, the peripheral must be able to
operate without the system clock. The interrupt source
must have the appropriate Interrupt Enable bit(s) set
prior to entering Sleep.
On waking from Sleep, if the GIE bit is also set, the
processor will branch to the interrupt vector. Otherwise,
the processor will continue executing instructions after
the SLEEP instruction. The instruction directly after the
SLEEP instruction will always be executed before
branching to the ISR. Refer to the 

for more details.

The INT pin can be used to generate an asynchronous
edge-triggered interrupt. This interrupt is enabled by
setting the INTE bit of the INTCON register. The
INTEDG bit of the OPTION_REG register determines on
which edge the interrupt will occur. When the INTEDG
bit is set, the rising edge will cause the interrupt. When
the INTEDG bit is clear, the falling edge will cause the
interrupt. The INTF bit of the INTCON register will be set
when a valid edge appears on the INT pin. If the GIE and
INTE bits are also set, the processor will redirect
program execution to the interrupt vector.

Upon entering an interrupt, the return PC address is
saved on the stack. Additionally, the following registers
are automatically saved in the Shadow registers:
• W register
• STATUS register (except for TO and PD)
• BSR register
• FSR registers
• PCLATH register
Upon exiting the Interrupt Service Routine, these regis-
ters are automatically restored. Any modifications to
these registers during the ISR will be lost. If modifica-
tions to any of these registers are desired, the corre-
sponding Shadow register should be modified and the
value will be restored when exiting the ISR. The
Shadow registers are available in Bank 31 and are
readable and writable. Depending on the user’s appli-
cation, other registers may also need to be saved.