From: Ullrich von Bassewitz (uz_at_musoftware.de)
Date: 2000-03-31 21:24:28
On Fri, Mar 31, 2000 at 08:31:25PM +0200, Martin Ancher Holm wrote:
> Over the last days, i've tried to make a macro to access kernel-calls.
> I've tried to use the #define statement.
>
> Can't I make a simple macro like #define kernel(function, a, x, y),
> instead of this for every function?
What you can do is:
--------------------------------------------------------------------------
unsigned char Y; /* We need a temporary storage */
#define kcall(name, a, x, y) \
Y = y; \
__AX__ = ((unsigned)(x) << 8) + (a); \
asm("\tldy\t_Y"); \
asm("\tjsr\t" #name);
--------------------------------------------------------------------------
One problem here is, that the names of the kernal functions are unknown. You
have to define them using asm() instructions, or use the address in hex.
As an example, to output a character, use
#define BSOUT(c) kcall($FFD2,c,0,0)
Calling
BSOUT('a');
Will then translate into the (inlined) code
lda #$00
sta _Y+0
ldx #$00
lda #$41
ldy _Y
jsr $FFD2
The loads and stores of y are useless in this case and can be avoided by using
a more specialized macro. The load of x cannot be avoided, because the
compiler is not smart enough.
There is also a C function called _sys (defined in 6502.h). The function is
able to call an arbitrary machine language subroutine, pass all registers and
the flags as parameters and return the register and flags after the call.
Because of the magic involved, the function is slower than using a specialized
macro to insert some lines of inline code.
Regards
Uz
--
Ullrich von Bassewitz uz_at_musoftware.de
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This archive was generated by hypermail 2.1.3 : 2001-12-14 22:05:36 CET