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Added more sample for the inline assembler. Contributed by Steffen Görzig.

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git-svn-id: svn://svn.cc65.org/cc65/trunk@5308 b7a2c559-68d2-44c3-8de9-860c34a00d81
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uz 2011-12-07 21:08:14 +00:00
parent 5449f21d9f
commit 494b0619d7
1 changed files with 48 additions and 2 deletions
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doc/cc65.sgml
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@ -1200,8 +1200,8 @@ the format specifier before passing the assembly code line to the backend.
<item><tt/%b/ - Numerical 8-bit value
<item><tt/%w/ - Numerical 16-bit value
<item><tt/%l/ - Numerical 32-bit value
<item><tt/%v/ - Assembler name of a (global) variable or function
<item><tt/%o/ - Stack offset of a (local) variable
<item><tt/%v/ - Assembler name of a global variable or function
<item><tt/%o/ - Stack offset of a local variable
<item><tt/%g/ - Assembler name of a C label
<item><tt/%s/ - The argument is converted to a string
<item><tt/%%/ - The % sign itself
@ -1229,6 +1229,52 @@ Or, to access a struct member of a static variable:
__asm__ ("lda %v,y", pixel);
</verb></tscreen>
<p>
The next example shows how to use global variables to exchange data between C
an assembler and how to handle assembler jumps:
<tscreen><verb>
unsigned char globalSubA, globalSubB, globalSubResult;
/* return a-b, return 255 if b>a */
unsigned char sub (unsigned char a, unsigned char b)
{
globalSubA = a;
globalSubB = b;
__asm__ ("sec");
__asm__ ("lda %v", globalSubA);
__asm__ ("sbc %v", globalSubB);
__asm__ ("bcs %g", jumpSubNoError);
__asm__ ("lda #$FF");
jumpSubNoError:
__asm__ ("sta %v", globalSubResult);
return globalSubResult;
}
</verb></tscreen>
<p>
Arrays can also be accessed:
<tscreen><verb>
unsigned char globalSquareTable[] = {
0, 1, 4, 9, 16, 25, 36, 49, 64, 81,
100, 121, 144, 169, 196, 225
};
unsigned char globalSquareA, globalSquareResult;
/* return a*a for a<16, else 255 */
unsigned char square (unsigned char a)
{
if (a>15){
return 255;
}
globalSquareA = a;
__asm__ ("ldx %v", globalSquareA);
__asm__ ("lda %v,x", globalSquareTable);
__asm__ ("sta %v", globalSquareResult);
return globalSquareResult;
}
</verb></tscreen>
<p>
Note: Do not embed the assembler labels that are used as names of global
variables or functions into your asm statements. Code like this