CCS C Compiler Manual PCB / PCM / PCH

parts. See the devices .h file for all valid interrupts for the part or in PCW use the pull
down VIEW | Valid Ints
The compiler will generate code to jump to the function when the interrupt is
detected. It will generate code to save and restore the machine state, and will clear the
interrupt flag. To prevent the flag from being cleared add NOCLEAR after the
#INT_xxxx. The application program must call ENABLE_INTERRUPTS(INT_xxxx) to
initially activate the interrupt along with the ENABLE_INTERRUPTS(GLOBAL) to
enable interrupts.
The keywords HIGH and FAST may be used with the PCH compiler to mark an interrupt
as high priority. A high-priority interrupt can interrupt another interrupt handler. An
interrupt marked FAST is performed without saving or restoring any registers. You
should do as little as possible and save any registers that need to be saved on your
own. Interrupts marked HIGH can be used normally. See #DEVICE for information on
building with high-priority interrupts.
A summary of the different kinds of PIC18 interrupts:
#INT_xxxx
Normal (low priority) interrupt. Compiler saves/restores key registers.
This interrupt will not interrupt any interrupt in progress.
#INT_xxxx FAST
High priority interrupt. Compiler DOES NOT save/restore key registers.
This interrupt will interrupt any normal interrupt in progress.
Only one is allowed in a program.
#INT_xxxx HIGH
High priority interrupt. Compiler saves/restores key registers.
This interrupt will interrupt any normal interrupt in progress.
#INT_xxxx NOCLEAR
The compiler will not clear the interrupt.
The user code in the function should call clear_interrput( ) to
clear the interrupt in this case.
#INT_GLOBAL
Compiler generates no interrupt code. User function is located
at address 8 for user interrupt handling.
Some interrupts shown in the devices header file are only for the enable/disable
interrupts. For example, INT_RB3 may be used in enable/interrupts to enable pin B3.
However, the interrupt handler is #INT_RB.
Similarly INT_EXT_L2H sets the interrupt edge to falling and the handler is #INT_EXT.
Examples:
#int_ad
adc_handler() {
adc_active=FALSE;
}
#int_rtcc noclear
isr() {
...
}
Example
See ex_sisr.c and ex_stwt.c for full example programs.
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