PIC18F2420/2520/4420/4520

DS80209D-page 8

© 2005 Microchip Technology Inc.

2. C Language Programming: The exact work

around depends on the compiler in use. Please

refer to your C compiler documentation for

details.

define both high and low priority interrupt han-

dler functions as “low priority” by using the

pragma interruptlow

directive.

This

directive instructs the compiler to not use the

RETFIE

FAST

instruction. If the proper high

priority interrupt bit is set in the IPRx register,

then the interrupt is treated as high priority in

spite of the pragma interruptlow directive.

The code segment shown in Example 3

demonstrates the work around using the C18

compiler:

EXAMPLE 3:

Date Codes that pertain to this issue:

All engineering and production devices.

#pragma interruptlow MyLowISR

void MyLowISR(void)

{

// Handle low priority interrupts.

}

// Although MyHighISR is a high priority interrupt, use interruptlow pragma so that

// the compiler will not use retfie FAST.

#pragma interruptlow MyHighISR

void MyHighISR(void)

{

// Handle high priority interrupts.

}

#pragma code highVector=0x08

void HighVector (void)

{

_asm goto MyHighISR _endasm

}

#pragma code /* return to default code section */

#pragma code lowVector=0x18

void LowVector (void)

{

_asm goto MyLowISR _endasm

}

#pragma code /* return to default code section */