Zilog Z8F0130 - Manual (Page 247)

UM013037-1212 Calling C Functions from Assembly
Zilog Developer Studio II – Z8 Encore!
User Manual
223
Calling C Functions from Assembly
The C functions that are provided with the compiler library can also be used to add func-
tionality to an assembly program. You can also create your own C functions and call them
from an assembly program.
In the C functions, all registers, other than return registers, are considered as caller save.
Therefore, the caller assembly function must make sure that it saves on the stack any reg-
isters that are in use before calling the C function and which also must be available after
the call. The caller assembly procedure then restores those registers after the return from
the C function. The flag register need not be saved and restored by the caller assembly
function.
The following example (the Assembly File section on page 224 and the Referenced C
Function Prototype section on page 224) shows an assembly source file referencing the
sin function written in the large, dynamic model. The sin function is defined in the C
run-time library ( crtldd.lib ).
The C-Compiler precedes the function names with an underscore in the generated assem-
bly. See the
Function Naming Convention section on page 221.
Note: