Zilog Z8F0130 - Manual (Page 245)

UM013037-1212 Calling Assembly Functions from C
Zilog Developer Studio II – Z8 Encore!
User Manual
221
and
•
The function does not return a structure.
and
•
The function is compiled without the debug option.
Calling Assembly Functions from C
The Z8 Encore! C-Compiler allows mixed C and assembly programming. A function writ-
ten in assembly can be called from C if the assembly function follows the C calling con-
ventions as described in the
Calling Conventions section on page 215.
This section covers the following topics:
•
Function Naming Convention – see page 221
•
Argument Locations – see page 221
•
Return Values – see page 222
•
Preserving Registers – see page 222
Function Naming Convention
Assembly function names must be preceded with an _ (underscore). The compiler prefixes
the function names with an underscore in the generated assembly. For example, a call to
myfunc() in C is translated to a call to _myfunc in generated assembly by the compiler.
Argument Locations
The assembly function must assign the location of the arguments following the C calling
conventions as described in the
Calling Conventions section on page 215.
For example, if you are using the following C prototype:
void myfunc(short arga, long argb, char argc, short * argd)
The location of the arguments must be as follows for a static frame function:
arga : _0_myfunc
argb: _1_myfunc
argc: _2_myfunc
argd: _3_myfunc
The location of the arguments must be as follows for a static frame function with register
parameter passing: