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Using OR in the argument for enable_interrupts()?

 
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lindsay.wilson.88



Joined: 11 Sep 2024
Posts: 40

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Using OR in the argument for enable_interrupts()?
PostPosted: Tue Sep 24, 2024 10:16 am     Reply with quote
Hi,

I'm probably being thick, but this caused me to tear my hair out for a good while!

In some functions, it's possible to combine multiple arguments/values with the | (or) operator - for example:

Code:
setup_timer_0 (TO_INTERNAL|TO_DIV2);


I then was trying to use enable_interrupts() to enable both global and timer 2 interrupts, and assumed that it would be possible to combine the two "levels" with an or operator again, i.e. like:

Code:
enable_interrupts(GLOBAL|INT_TIMER2);


However, this doesn't work. Looking at the listing, it writes to the TOSU register (something about the stack, I'm not sure). Whereas, if I do separate:

Code:
enable_interrupts(INT_TIMER2);
enable_interrupts(GLOBAL);


these write to PIE1 and INTCON, as I'd expect. And, the interrupts then work.

Could someone please clarify all this? Am I mistaken about combining arguments in this way?

Thanks,

Lindsay
Ttelmah



Joined: 11 Mar 2010
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PostPosted: Tue Sep 24, 2024 12:24 pm     Reply with quote
It's down to the nature of the settings. The former is a value that sets
bits in one or more registers. These can be or'ed (and if you look at
the remarks for these values, the .h file tells you this). Howeevr the
interrupt setting is a specific value with a specific meaning. Each interrupt
has a specific numeric code, and or'ing these will set somthing completely
different.
lindsay.wilson.88



Joined: 11 Sep 2024
Posts: 40

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PostPosted: Tue Sep 24, 2024 7:10 pm     Reply with quote
Ahhh, that makes sense now, thanks!
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