PicC 9.50 dsPIC Manual.pdf

Mixing C and Assembler CodeC Language Featuresextern unsigned int add(unsigned a, unsigned b);void main(void){int a, result;a = read_port();result = add(5, a);}3.11.2 #asm, #endasm and asm()dsPIC instructions may also be directly embedded “in-line” into C code using the directives #asm,#endasm or the statement asm().The #asm and #endasm directives are used to start and end a block of assembly instructions whichare to be embedded into the assembly output of the code generator. The #asm and #endasm constructis not syntactically part of the C program, and thus it does not obey normal C flow-of-control rules,however you can easily include multiple instructions with this form of in-line assembly.The asm() statement is used to embed a single assembler instruction. This form looks and behaveslike a C statement, however each instruction must be encapsulated within an asm() statement.•You should not use a #asm block within any C constructs such as if, while, do etc.In these cases, use only the asm("") form, which is a C statement and will correctlyinteract with all C flow-of-control structures.The following example shows both methods used:52unsigned int var;void main(void){var = 1;#asm// like this...mov.w _var,w0sl.w w0,w0mov.w w0,_var#endasm// or like this