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-<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>
-
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-<LI><A NAME="tex2html896"
- HREF="node42.html#SECTION00054100000000000000">4.4.1 Global Registers used for Parameter Passing</A>
-<LI><A NAME="tex2html897"
- HREF="node42.html#SECTION00054200000000000000">4.4.2 Assembler Routine(non-reentrant)</A>
-<LI><A NAME="tex2html898"
- HREF="node42.html#SECTION00054300000000000000">4.4.3 Assembler Routine(reentrant)</A>
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-
-<H2><A NAME="SECTION00054000000000000000">
-4.4 Interfacing with Assembly Routines</A>
-</H2>
-
-<P>
-
-<H3><A NAME="SECTION00054100000000000000">
-4.4.1 Global Registers used for Parameter Passing</A>
-</H3>
-
-<P>
-The compiler always uses the global registers <I>DPL,DPH,B</I> and
-<I>ACC</I> to pass the first parameter to a routine. The second parameter
-onwards is either allocated on the stack (for reentrant routines or
-if -stack-auto is used) or in the internal / external ram (depending
-on the memory model).
-
-<P>
-
-<H3><A NAME="SECTION00054200000000000000">
-4.4.2 Assembler Routine(non-reentrant)</A>
-</H3>
-
-<P>
-In the following example the function cfunc calls an assembler routine
-asm_func, which takes two parameters.
-<BR>
-
-<BR>
-<TT>extern int asm_func(unsigned char, unsigned char);</TT>
-<BR>
-<BR>
-<TT>int c_func (unsigned char i, unsigned char j)</TT>
-<BR>
-<TT>{</TT>
-<BR>
-<TT> return asm_func(i,j);</TT>
-<BR>
-<TT>}</TT>
-<BR>
-<BR>
-<TT>int main()</TT>
-<BR>
-<TT>{</TT>
-<BR>
-<TT> return c_func(10,9);</TT>
-<BR>
-<TT>}</TT>
-<BR>
-<BR>
-The corresponding assembler function is:
-<BR>
-
-<BR>
-<TT>.globl _asm_func_PARM_2 </TT>
-<BR>
-<TT> .globl _asm_func </TT>
-<BR>
-<TT> .area OSEG </TT>
-<BR>
-<TT>_asm_func_PARM_2:</TT>
-<BR>
-<TT> .ds 1 </TT>
-<BR>
-<TT> .area CSEG </TT>
-<BR>
-<TT>_asm_func: </TT>
-<BR>
-<TT> mov a,dpl </TT>
-<BR>
-<TT> add a,_asm_func_PARM_2 </TT>
-<BR>
-<TT> mov dpl,a </TT>
-<BR>
-<TT> mov dpl,#0x00 </TT>
-<BR>
-<TT> ret</TT>
-<BR>
-<BR>
-Note here that the return values are placed in 'dpl' - One byte return
-value, 'dpl' LSB & 'dph' MSB for two byte values. 'dpl', 'dph' and
-'b' for three byte values (generic pointers) and 'dpl','dph','b' &
-'acc' for four byte values.
-
-<P>
-The parameter naming convention is _<function_name>_PARM_<n>,
-where n is the parameter number starting from 1, and counting from
-the left. The first parameter is passed in ``dpl'' for One bye
-parameter, ``dptr'' if two bytes, ``b,dptr'' for three bytes
-and ``acc,b,dptr'' for four bytes, the varible name for the second
-parameter will be _<function_name>_PARM_2.
-<BR>
-
-<BR>
-Assemble the assembler routine with the following command:
-<BR>
-
-<BR>
-<I><B>asx8051 -losg asmfunc.asm</B></I>
-<BR>
-<BR>
-Then compile and link the assembler routine to the C source file with
-the following command:
-<BR>
-
-<BR>
-<I><B>sdcc cfunc.c asmfunc.rel</B></I>
-
-<P>
-
-<H3><A NAME="SECTION00054300000000000000">
-4.4.3 Assembler Routine(reentrant)</A>
-</H3>
-
-<P>
-In this case the second parameter onwards will be passed on the stack,
-the parameters are pushed from right to left i.e. after the call the
-left most parameter will be on the top of the stack. Here is an example:
-<BR>
-
-<BR>
-<TT>extern int asm_func(unsigned char, unsigned char);</TT>
-<BR>
-<BR>
-<TT>int c_func (unsigned char i, unsigned char j) reentrant </TT>
-<BR>
-<TT>{ </TT>
-<BR>
-<TT> return asm_func(i,j); </TT>
-<BR>
-<TT>} </TT>
-<BR>
-<BR>
-<TT>int main() </TT>
-<BR>
-<TT>{ </TT>
-<BR>
-<TT> return c_func(10,9); </TT>
-<BR>
-<TT>}</TT>
-<BR>
-
-<BR>
-The corresponding assembler routine is:
-<BR>
-
-<BR>
-<TT>.globl _asm_func </TT>
-<BR>
-<TT>_asm_func: </TT>
-<BR>
-<TT> push _bp </TT>
-<BR>
-<TT> mov _bp,sp </TT>
-<BR>
-<TT> mov r2,dpl</TT>
-<BR>
-<TT> mov a,_bp </TT>
-<BR>
-<TT> clr c </TT>
-<BR>
-<TT> add a,#0xfd </TT>
-<BR>
-<TT> mov r0,a </TT>
-<BR>
-<TT> add a,#0xfc</TT>
-<BR>
-<TT> mov r1,a </TT>
-<BR>
-<TT> mov a,@r0 </TT>
-<BR>
-<TT> add a,r2</TT>
-<BR>
-<TT> mov dpl,a </TT>
-<BR>
-<TT> mov dph,#0x00 </TT>
-<BR>
-<TT> mov sp,_bp </TT>
-<BR>
-<TT> pop _bp </TT>
-<BR>
-<TT> ret</TT>
-<BR>
-<BR>
-The compiling and linking procedure remains the same, however note
-the extra entry & exit linkage required for the assembler code, _bp
-is the stack frame pointer and is used to compute the offset into
-the stack for parameters and local variables.
-
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-<ADDRESS>
-<I>Johan Knol</I>
-<BR><I>2001-07-13</I>
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