AN3350 datasheet(70/185 Pages) STMICROELECTRONICS

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Working with the assembler

AN3350

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Doc ID 018512 Rev 2

The #assign directive

#assign <name> <numeric expression>

first deletes the macro and then redefines it as if defined using

#xdefine <name> %eval(<numeric expression>)

An example of this is shown in Example 9 .

Example 9 Using the #assign directive

#define XXX 1

#assign XXX 2

#assign XXX XXX + 1

#assign XXX YYY ; invalid

The first three lines above will assign macro XXX the values 1, 2, and 3 respectively. The

last line is invalid since the defining expression is not a numeric constant.

10.6.1

Conditional assembly

The assembler can assemble code portions in order to fulfill conditions set by the user

conditions defined with clausal directives similar to the if statement of the C program, as

shown in Example 10.

Example 10 Assembler directives

#if {condition1}

// this code is processed only if condition1 is true

#elif {condition2}

// this code is processed if condition1 is false and

// condition2 is true

#macro

Begins the definition of a multi-line macro. As macro names can

override special identifiers, you can create macros that replace

ordinary instructions. Single- and multi-lined macros share the

same name space; so only one macro type can exist for an

identifier.

#rmdef

Deletes all user macro definitions. Effect the same as using the

#undef

directive on all existing user macros.

#undef

Use this directive to reverse the effect of a #define, #xdefine, or

#macro

directive, cancelling any definitions made for an identifier.

For example, #undef XYZ causes the assembler not to expand

further references to the term XYZ.

#xdefine

Similar to the #define directive, except that the assembler does

not postpone definition expansion until the macro is invoked.

Instead, the assembler expands the definition at compile time.

Table 8.

Macro-related directives (continued)

Directive

Explanation

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