UM0144 datasheet(27/92 Pages) STMICROELECTRONICS

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UM0144

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The true use of macros is in small snippets of code that you use repeatedly— perhaps with

different arguments—which can be formalized into a 'template' for the macros' definition.

3.5.1

Defining macros

Macros are defined using three directives: MACRO, MEND and LOCAL.

The format is:

<macro-name>MACRO

[parameter-1][, parameter-2 ...]

[LOCAL] <label-name>[, label-name ...]]

<body-of-macro>

MEND

For example:

The piece of code of the example might be called by:

add16 index,offset,index

which would add the following statements to the source code at that point:

ld A,index

adc A,offset

ld index.X,A

Note that the formal parameters given in the definition have been replaced by the actual

parameters given on the calling line. These new parameters may be expressions or strings

as well as label names or constants. Because they may be complex expressions, they are

bracketed when there is any extra numeric activity; this is to make sure they come out with the

precedence correctly parsed.

Macros do not need to have any parameters. You may leave the MACRO argument field blank

(and, in this case, give no parameters on the calling line).

There is one further problem: because a macro may be called several times in the same

module, any labels defined in the macro will be duplicated. The LOCAL directive gets around

this problem:

add16

MACRO first,second,result

ld A,first

adc A,second

ld result,A

MEND

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