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You can easily interface your C programs to routines written in assembly language. By following a few programming rules, you can call assembly routines from C and vice versa. Public variables declared in the assembly module are available to your C programs.
There are several reasons why you may need to call an assembly routine from your C program.
- You have assembly code already written that you wish to use.
- You need to improve the speed of a particular function.
- You want to manipulate Peripheral Registers or memory-mapped I/O devices directly from assembly.
This section describes how to write assembly routines that can be directly interfaced to C programs.
For an assembly routine to be called from C, it must be aware of the parameter passing and return value conventions used in C functions. For all practical purposes, the assembly routine must appear to be a C function.
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