How to define an interrupt in PIC18F?

Question

The PIC18F family I guess has high and low priority interrupt-service-routines, not just one ISR. My first time dealing with this and I can't seem to get the compiler (XC8) to recognize the two difference interrupts from some legacy code. Basically, I don't know where to look when hoping to figure out what to tell the compiler to mark these two functions as interrupts?

#include <xc8.h>
...
__interrupt(high_priority) void MyHighPriorityIsr(void)
{
// stuff
}
__interrupt(low_priority) void MyLowPriorityIsr(void)
{
// stuff
}

I'm getting:

error: (285) no identifier in declaration
error: (1275) only functions may be qualified "interrupt"

Page 34 of the compiler's user guide make it seem fine, but I'm getting errors and can't compile: http://ww1.microchip.com/downloads/en/DeviceDoc/MPLAB_XC8_C_Compiler_User_Guide.pdf

• Leon Heller: He said it's XC8!
• Matt Young: @LeonHeller After I asked him...
• derlo: tarabyte, So are you satisfied with the answers or not. If not let me know exactly what processor are you using, so that I can check that my solution will work for you. I use PIC18F46K20 with LOW and HIGH priority interrupts, under XC8 compiler ver 1.30 and MPLAB 8.76 and all works fine, code compiles and actually does what it is supposed to do (ADC Ints, TMR0 and TMR1 Ints, Ints on pin change (IOCB)). But I must admit it took me hours to figure out which bits in which registers to set and which form of ISR def/decl to use. XC8 manual is too generic. They should have abandoned C18 legacy and n

Answer 1

void low_priority interrupt Low_Priority_Interrupt(void) {
 if (TMR1IE && TMR1IF) {
 TMR1H = 0xFE;//Pre load for 125 ms
 Timer1_Isr();
 TMR1IF = 0;
 return;
 }
}
void high_priority interrupt High_Priority_Interrupt(void) {
 if (TX2IE && TX2IF) {
 SerialTx_Isr();
 TX2IF = 0;
 return;
 }
 if (RC2IE && RC2IF) {
 SerialRx_Isr();
 RC2IF = 0;
 return;
 }
}

Answer 2

Is it possible that you aren't declaring your functions properly?

Higher in your code, you should have the declarations:

void __interrupt(high_priority) MyHighPriorityIsr(void);
void __interrupt(low_priority) MyLowPriorityIsr(void);

Then, later, your function definitions:

void __interrupt(high_priority) MyHighPriorityIsr(void)
{
// stuff
}
void __interrupt(low_priority) MyLowPriorityIsr(void)
{
// stuff
}

Also, notice that "void" comes before __interrupt()

Good luck!

• tarabyte: all the permutations of where i place __interrupt seem to not allow me to compile :(
• Matt Young: That is not the XC8 way of writing ISRs.
• bitsmack: @MattYoung I believe you, since it didn't work for terabyte. But, i took it directly from the the XC Users Guide (version D), section 2.5.10.3. For example, it says that for 8-bit compilers, to change void interrupt myIsr(void) to void __interrupt(high_priority) myIsr(void) and to change void interrupt low_priority myLoIsr(void) to void __interrupt(low_priority) myLoIsr(void). I copied and pasted... Could you let me know how it should be done? I haven't migrated from Microchip's C18 yet :)
• Matt Young: What Eric Friesen said. The pertinent part of the XC8 manual is section 5.9. And stick with C18, XC8 is inferior.
• Erik Friesen: I don't like either. They have oddities that are annoying after using c32.