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Altera_Forum's avatar
Altera_Forum
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20 years ago

Inline assembly code / Nios II Project

All:

I am trying to write a simple program as part of an Altera Nios II application in which I want to embed a few lines of assembly code

Can anyone provide me with an example of how this is done?

I have tried a number of ways of using the asm / volatile keywords as normally used but cannot get the program to compile without errors.

If this is actually supported, a simple example will suffice.

Thanks

Nick

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    20 years ago

    Hi Nick,

    > If this is actually supported

    It is.

    > a simple example will suffice.

    Here are a few:

    write a byte to i/o (bypass cache)
    #define readb(addr)
    (    {  unsigned char val;
          asm volatile( "ldbio %0, 0(%1)" :"=r"(val) : "r" (addr)); val;}
)

    read/write the control register
    #define CTL_STATUS    0  /* Processor status reg  */# define CTL_ESTATUS    1  /* Exception status reg  */# define CTL_BSTATUS    2  /* Break status reg  */# define CTL_IENABLE    3  /* Interrut enable reg  */# define CTL_IPENDING    4  /* Interrut pending reg  */
# define _str_(x)# x
# define rdctl(reg)
    (    {unsigned int val;
         asm volatile( "rdctl %0, ctl" _str_(reg) : "=r" (val) ); val;}
)
# define wrctl(reg,val)
    asm volatile( "wrctl ctl" _str_(reg) ",%0": : "r" (val))
/* E.g.: foo = rdctl(CTL_IENABLE);
 *          wrctl(CTL_IENABLE, foo | 1);
 */

    Regards,

    --Scott
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    20 years ago

    Hi Scott:

    Thanks for the reply!

    I wound up going through some Linux kernel driver files and taking some examples from there.

    Actually though, the ones you provided are best for me since I am working with the rdctl and wrctl commands.

    Thanks Again!

    Nick