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7.5
Macro Control Statements
Macro control statements reduce coding effort by replacing strings coded in source statements with other
strings. This enables low-level assembly language for a program block to be abstracted as a macro
name.
Macros are coded in two formats: macro definitions and macro calls.
A macro definition defines a macro name and macro body. The macro body uses multiple machine lan-
guage instructions to construct a single program process.
A macro call is just a macro name coded as a source statement. The assembler will replace it with all
the machine language instructions coded in the macro body. This process is called macro expansion.
The basic difference between a macro call and a subroutine call is that a macro call actually outputs ma-
chine language instructions as source statements, with arguments used to output different machine lan-
guage instructions for each call.
The example below shows macro control statements.
*macro definition-------------------------------
adr_set
*macro call-------------------------------------
macro
data, reg
mov
reg, A0
mov
data, D0
mov
D0, (A0)
endm
.
.
.
adr_set
.
.
.
adr_set
.
.
.
Chapter 7 Type of Source Statements
data1, reg1
data2, reg2
Macro Control Statements 123
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