Motorola HC12 - Manual (Page 182)

User’s Manual MCUez HC12 Assembler
182 Assembler Directives MOTOROLA
Assembler Directives
8.17 IF — Conditional Assembly
Syntax: IF <condition>
[<assembly language statements>]
[ ELSE ]
[<assembly language statements>]
ENDIF
Description: If <condition> is true, the statements immediately following
the
IF directive generate code. Assembly continues until the
corresponding ELSE or ENDIF directive is reached. Then all
statements until the corresponding ENDIF directive are
ignored. Nesting of conditional blocks is allowed. The
maximum level of nesting is limited by available memory at
assembly time.
The expected syntax for <condition> is:
<condition> := <expression> <relation> <expression>
<relation> := "=" | "!=" | " >=" | ">" | "<=" | "<" | "<>"
The <expression> must be absolute. It must be known at
assembly time.
Example:
This is an example of using conditional assembly directives:
Try: EQU 0
IF Try != 0
LDD #1023
ELSE
LDD #0
ENDIF
The value of TRY determines the instruction that generates
code. As shown, the LDD #0 instruction generates code.
Changing the operand of the EQU directive to one causes the
LDD #1023 instruction to generate code instead.
This is the listing provided by the assembler for these lines of code:
0000 0000 Try: EQU 0
0000 0000 IF Try != 0
ELSE
000000 CC 0000 LDD #0
ENDIF