Texas Instruments TMS320C54x, User Manual

Page: 167 / 469

.struct/.endstruct/.tag
Declare Structure Type
4-84
Syntax
[ stag ] .struct [ expr ]
[ mem
0
] element [ expr
0
]
[ mem
1
] element [ expr
1
]
. . .
. . .
. . .
[ mem
n
] .tag stag [, expr
n
]
. . .
. . .
. . .
[ mem
N
] element [ expr
N
]
[ size ] .endstruct
label
.tag
stag
Description The .struct directive assigns symbolic offsets to the elements of a data struc-
ture definition. This enables you to group similar data elements together and
then let the assembler calculate the element offset. This is similar to a C
structure or a Pascal record. A .struct definition may contain a .union definition,
and .structs and .unions may be nested. The .struct directive does not allocate
memory; it merely creates a symbolic template that can be used repeatedly.
The .endstruct directives terminates the structure definition.
The .tag directive gives structure characteristics to a label, simplifying the
symbolic representation and providing the ability to define structures that con-
tain other structures. The .tag directive does not allocate memory. The struc-
ture tag (stag) of a .tag directive must have been previously defined.
stag
is the structure’s tag. Its value is associated with the beginning
of the structure. If no stag is present, the assembler puts the
structure members in the global symbol table with the value of
their absolute offset from the top of the structure. Stag is optional
for .struct, but required for .tag.
expr is an optional expression indicating the beginning offset of the
structure. Structures default to start at 0.