View source for Writing interruptible code on C6xxx DSPs

Taken from document SPRA534.pdf by Texas Instruments: Writing Interruptible Looped Code for the TMS320C6x DSP

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== compiler option –mi''n'' ==

The C6x code generation tools provide a high degree of flexibility for interruptibility. The
compiler option –mi''n'' specifies an optional interrupt threshold value, ''n''.  The threshold
value specifies the maximum number of clock cycles that the compiler can disable
interrupts. When using the –mi''n'' option, the compiler and assembly optimizer analyze
both the loop structure and the number of times the loop will be iterated to determine the
maximum number of cycles it will take to execute the loop. If the tools can determine that
the maximum number of cycles is less than the threshold value, the compiler/assembly
optimizer will create non-interruptible code.  Otherwise, the tools generate interruptible
looped code that will, in most cases, not degrade the performance of that loop.
The compiler command line option –mi''n'' can be used for an entire module.  


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== pragma FUNC_INTERRUPT_THRESHOLD ==

In addition, a pragma can be used to specify the threshold on a function-by-function basis.  This
pragma is of the form:


<syntaxhighlight lang="c">
#pragma FUNC_INTERRUPT_THRESHOLD(func, threshold);
</syntaxhighlight>

or for c++:

<syntaxhighlight lang="c">
#pragma FUNC_INTERRUPT_THRESHOLD(threshold);
</syntaxhighlight>


The #pragma overrides the –mi''n'' command line option.  If a threshold of less than 0 is
specified, it is assumed that the function will never be interrupted.


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== Examples ==
===  –mi''n''===
Compiler option -mi50 means, all loops in the current module must be interruptible after 50 cycles.


=== FUNC_INTERRUPT_THRESHOLD ===

The following examples demonstrate the use of different thresholds:
* The function foo() must be interruptible at least every 2,000 cycles:

<syntaxhighlight lang="c">
#pragma FUNC_INTERRUPT_THRESHOLD(foo,2000)
</syntaxhighlight>


* The function foo() must always be interruptible.
<syntaxhighlight lang="c">
#pragma FUNC_INTERRUPT_THRESHOLD(foo,1)
</syntaxhighlight>


* The function foo() is never interrupted.
<syntaxhighlight lang="c">
#pragma FUNC_INTERRUPT_THRESHOLD(foo,-1)
</syntaxhighlight>


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== Additional Tags ==
spru187o.pdf, spru425a.pdf

 [[category:Software]]