Motorola HC12 User Manual
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.
<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
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.
restored to the next available location in this section.