Texas Instruments TMS320C54x, User Manual

Page: 195 / 469

Using Conditional Assembly in Macros
5-15 Macro Language
5.5 Using Conditional Assembly in Macros
The conditional assembly directives are .if/.elseif/.else/.endif and .loop/
.break/.endloop. They can be nested within each other up to 32 levels deep.
The format of a conditional block is:
.if
well-defined expression
[.elseif well-defined expression]
[.else well-defined expression]
.endif
The .elseif and .else directives are optional, and they can be used more than
once within a conditional assembly code block. When .elseif and .else are
omitted, and when the .if expression is false (0), the assembler continues to
the code following the .endif directive. For more information on the .if/
.elseif/.else/.endif directives, see page 4-56.
The .loop/.break/.endloop directives enable you to assemble a code block
repeatedly. The format of a repeatable block is:
.loop [well-defined expression]
[.break [ well-defined expression]]
.endloop
The .loop directive’s optional expression evaluates to the loop count (the
number of loops to be performed). If the expression is omitted, the loop count
defaults to 1024 unless the assembler encounters a .break directive with an
expression that is true (nonzero). For more information on the .loop/
.break/.endloop directives, see page 4-65.
The .break directive and its expression are optional. If the expression
evaluates to false, the loop continues. The assembler breaks the loop when
the .break expression evaluates to true or when the .break expression is
omitted. When the loop is broken, the assembler continues with the code after
the .endloop directive.
Example 5–10, Example 5–11, and Example 5–12 show the .loop/.break/
.endloop directives, properly nested conditional assembly directives, and
built-in substitution symbol functions used in a conditional assembly code
block.