interrupt priority changed by compiler?

[Ramey]

In my program I have used

#int_timer0 high

When I do this - I get another warning. This suggests that now I have 2 high priority interrupts - timer0 + USB which I don't want as it is critical to me that the timer0 be invoked "on time".

What can/should I do to fix this.

Robert Ramey

[Guest_7068]

There is a compiler directive which you can use to set the priority in which the compiler checks the interrupt flags:

[Ttelmah]

No.
#priority, only changes the order the flags are scanned in the individual global handler (a sort of psuedo priority, that 'pre-dates' the hardware priority on latter chips). What is happening, is that the compiler insists on the USB interrupts, being raised to the 'high' hardware priority, if the hardware priority ability is used. It is really a fault, and should be reported to CCS. Ideally, while this is probably a 'safer' default behaviour, if people write slow 'high priority' handlers, there should be an option to disable this.
There are some behaviours of this sort, that are in the hardware (for instance, on most chips, if the hardware high priority interrupts are enabled, INT_RTCC, will automatically be promoted to become a high priority interrupt, but there is no such hardware limitation on the USB interrupt.
It appears that CCS are just being a little 'too smart' here...

Best Wishes

[OzanGazi]

Yes I have the same problem..

device 18f8722.in my program i am using

#int_timer1
#int_timer3
#int_rda high
#int_rda2 high
#int_adc
#int_ext

There is no problem except #int_ext

Warning 225 : Interrupt level changed EXT : NORMAL => HIGH

[Ttelmah]

It is not the compiler doing the change.
It is just warning you that this is happening.

Read the data sheet.
Study the interrupt tree.
Look at the INT0 interrupt. Do you see a INT0IP bit?.

This is common for all the PC18 chips. INT_EXT, has no priority flag in the hardware, and is _always_ a high priority interrupt, if hardware priority is enabled.

Paragraph 10.6 in the data sheet. Last line:
"There is no priority bit associated with INT0.
It is always a high priority interrupt source."

If you want a low priority external interrupt, you have to use INT1,2 or 3.

Best Wishes

[OzanGazi]

Thank you Ttelmah everything is clear...Now i am using INT1 and no problem..