mixing C and assembly.

[Joel Sherrill]

Salim Belgroune wrote:

> Hello,
> 
> I'm currently using the MPC8260  ( with a PPC 603e core ).
> 
> Could you give me a tutorial or examples on writing assembly routines 
> that will be written and compiled inside a C source code.

There are no tutorials that I know of.  There are sources for examples
including the PowerPC specific code in RTEMS.  Here is an example
of disabling external interrupts via the MSR:

#define _CPU_ISR_Disable( _isr_cookie ) \
   { register unsigned int _disable_mask = PPC_MSR_DISABLE_MASK; \
     _isr_cookie = 0; \
     asm volatile ( \
         "mfmsr %0; andc %1,%0,%1; mtmsr %1" : \
         "=&r" ((_isr_cookie)), "=&r" ((_disable_mask)) : \
         "0" ((_isr_cookie)), "1" ((_disable_mask)) \
         ); \
   }

It returns the previous value of the MSR as "_isr_cookie" so you
can enable later to the previous level:

#define _CPU_ISR_Enable( _isr_cookie )  \
   { \
      asm volatile ( "mtmsr %0" : \
                    "=r" ((_isr_cookie)) : \
                    "0" ((_isr_cookie))); \
   }

There are lots of other examples in the RTEMS source.

> Kind regards.
> 
> Salim Belgroune.
> 


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Joel Sherrill, Ph.D.             Director of Research & Development
joel@OARcorp.com                 On-Line Applications Research
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