Pic 24FJ instruction DISI

[rogerp2]

Is there a built-in function in picc-d that sets and uses the DISI instruction for this processor family?

Thanks

[Ttelmah]

It is used throughout the generated code, but to generate it yourself, you
would simply have to use assembler.
It would be almost impossible to use inside normal C code, since you do not
have any ability to know how many instructions a C code line actually uses.
So like this:

[temtronic]

OK, curious am I,
Why would you need to use it ?
I had a quick read and it only disables some interrupts(based on 'level') and ONLY for a finite time( 16383 machine cycles), so the 'time' isn't fixed...change the CPU speed and the DISI time changes as well.
I'd think the CCS supplied functions would work for 99.44% of all applications ??

[rogerp2]

Hi Ttelmah

Thanks. Whereas I agree it is difficult to determine how many cycles a chunk of C code uses (read the .lst file), there is another way:

#asm
disi #16383
#endasm
C code to be protected
#asm
disi #0
#endasm

That does work.

Roger Pryor

[rogerp2]

Hi temtronic

Curiosity solved - The short answer is that I'm mucking about with interrupts and code functions used both in ISR and the main line. This instruction is actually very powerful when trying to avoid lockups. The long answer is much longer and not of general interest.

Thanks anyway

Roger Pryor

[Ttelmah]

If you are fiddling around doing it twice, then just use a standard
disable_interrupts call. You do understand that you can specify what level
of disable is to be applied.
It is a pointless approach.

[jeremiah]

[Ttelmah]

Yes, I use this library for certain hardware transactions that have to be
'atomic'. Works well. There are a few little 'syntactical sneakies', that
have to be used if the flow through the code can have multiple paths,
but with a bit of care it is a very good way of working.