Assembly Language Quick Guide

Keep these rules in mind as you write assembly language functions:

• Each statement must be a label or a function.
• A label can be any identifier not already declared as a local variable.
• All labels must follow the syntax:

  [LocalLabel:]

  The following listing illustrates the use of labels.

  Listing: Labels in M56800E assembly

  x1:  add  x0,y1,a  
  
  x2:                   
  
       add  x0,y1,a 
  
  x3   add  x0,y1,a  //ERROR, MISSING COLON
  

• All instructions must follow the syntax:

  ( (instruction) [operands] )

• Each statement must end with a new line
• Assembly language directives, instructions, and registers are not case-sensitive. The following two statements are the same:

  add x0,y0

  ADD X0,Y0

• Comments must have the form of C or C++ comments; they must not begin with the ; or # characters. The following listing shows the valid syntax for comments.
  Listing: Valid comment syntax

      move.w    x:(r3),y0     #  ERROR
  
      add.w     x0,y0         // OK
  
      move.w    r2,x:(sp)     ; ERROR
  
      adda    r0,r1,n       /* OK */
  

• To optimize a block of inline assembly source code, use the inline assembly directive .optimize_iasm on before the code block. Then use the directive .optimize_iasm off at the end of the block. (Omitting .optimize_iasm off means that optimizations continue to the end of the function.)