#priority

[BLL]

Hi, In a recent project with an 18F2550, I was able to use the #priority directive to prioritise interrupts.

My current project uses an 18LF2620 at 10MHz on 3.3V. When I include the #priority directive, the compiler says "invalid preprocessor directive".

However the datasheets of both devices says the interrupts can be prioritised.

What am I doing wrong and how do you set their priorities?

PCWH v3.249

[asmboy]

have you used the search feature of the forum?

i believe your answer is there.

i searched on the term
#PRIORITY
and liked what i found

wisdom in there ...

[PCM programmer]

If I compile a test program with only a main() and just #priority, I get
this message from a modern version of the compiler:

[BLL]

Yes, I did search the forum and didn't find the answer. If I had, I wouldn't have posted the question!!

[Ttelmah]

First, 'priority' has nothing to do with the PIC 18 chip's hardware priority.

All it does is set the order in which interrupts are 'scanned' in the global handler. It won't allow an interrupt to interrupt another.

It'll only work, with some interrupt names.

If (for instance), you have INT_RDA, and INT_EXT, then:

[ckielstra]

Update: I see Ttelmah posted an answer while I was typing mine. For extra info I'll have it here as it is.

The hint you were given is that the error message you list does not match the code as you describe it.

One golden rule on this forum is that for the best response you should always post an example program demonstrating your problem. Make the program small, about 10 lines, and complete including the #fuses line so we can copy/paste it into our compiler.
Often when creating the tiny program you will discover the problem cause yourself.

In your project I suspect a small syntax error.

Also from your description I notice that you misunderstand how to configure the interrupt priorities. Your processor has hardware support for two interrupt levels: normal and high.
The processor's #priority directive has nothing to do with these hardware priorities. #priority is used for the special case where two interrupts of the same hardware interrupt priority occur at exactly the same moment. In that special case you can define which priority is placed higher in the list of the (software based) interrupt dissector. In my opinion an (almost) useless compiler directive. Interrupts should be handled as fast as possible, meaning that never 1 interrupt can be missed. Having designed your software that way there is no need for handling this special case.

By default the compiler sets all interrupts at the 'normal' hardware level. You create a 'high' level interrupt by adding the keyword 'HIGH':

[BLL]

Thank you both for your replies which have made matters much clearer. I found the reason for the error message as I had used int_rda instead of just rda!