Motorola HC12 - Manual (Page 194)

User’s Manual MCUez HC12 Assembler
194 Assembler Directives MOTOROLA
Assembler Directives
8.29 OFFSET — Create Absolute Symbols
Syntax: OFFSET <expression>
Description: The OFFSET directive declares an offset section and initializes
the location counter to the value specified in <expression>. The
<expression> must be absolute and may not contain references
to external, undefined, or forward defined labels.
The OFFSET section is useful to simulate data structure or a
stack frame.
Example: The following example shows how OFFSET can be used to
access elements of a structure.
6 6 OFFSET 0
7 7 000000 ID: DS.B 1
8 8 000001 COUNT: DS.W 1
9 9 000003 VALUE: DS.L 1
10 10 0000 0007 SIZE: EQU *
11 11
12 12 DataSec: SECTION
13 13 000000 Struct: DS.B SIZE
14 14
15 15 CodeSec:SECTION
16 16 entry:
17 17 000003 CE xxxx LDX #Struct
18 18 000006 8600 LDAA #0
19 19 000008 6A00 STAA ID, X
20 20 00000A 6201 INC COUNT, X
21 21 00000C 42 INCA
22 22 00000D 6A03 STAA VALUE, X
As soon as a statement affecting the location counter (other
than
EVEN , LONGEVEN , ALIGN , or DS ) is encountered after
the OFFSET directive, the offset section is ended. The
preceding section is activated again, and the location counter is
restored to the next available location in this section.