Symbols
3-18
3.8
Symbols
Symbols are used as labels, constants, and substitution symbols. A symbol
name is a string of up to 200 alphanumeric characters (A – Z, a – z, 0 – 9, $,
and _ ). The first character in a symbol cannot be a number, and symbols can-
not contain embedded blanks. The symbols you define are case sensitive; for
example, the assembler recognizes ABC, Abc, and abc as three unique
symbols. You can override case sensitivity with the – c assembler option. A
symbol is valid only during the assembly in which it is defined, unless you use
the .global directive to declare it as an external symbol.
3.8.1
Labels
Symbols used as labels become symbolic addresses associated with loca-
tions in the program. Labels used locally within a file must be unique.
Mnemonic opcodes and assembler directive names (without the ”.” prefix) are
valid label names.
Labels can also be used as the operands of .global, .ref, .def, or .bss directives;
for example:
.global
label1
label2
NOP
ADD
label1,B
B
label2
3.8.2
Symbolic Constants
Symbols can be set to constant values. By using constants, you can equate
meaningful names with constant values. The .set and .struct/.tag/.endstruct
directives enable you to set constants to symbolic names. Symbolic constants
cannot be redefined. The following example shows how these directives can
be used:
K
.set
1024
;constant definitions
maxbuf .set
2*K
value
.set
0
.
delta
.set
1
.
item
.struct
;item structure definition
.int
value
;constant offsets value = 0
.int
delta
;constant offsets delta = 1
i_len
.endstruct
array
.tag
item
;array declaration
.bss
array, i_len*K
The assembler also has several predefined symbolic constants; these are
discussed in the next section.
Summary of Contents for TMS320C54x
Page 38: ......
Page 39: ......
Page 40: ......
Page 41: ......
Page 42: ......
Page 43: ......
Page 44: ......
Page 45: ......
Page 46: ......
Page 47: ......
Page 48: ......
Page 49: ......
Page 50: ......
Page 51: ......
Page 52: ......
Page 53: ......
Page 54: ......
Page 55: ......
Page 56: ......
Page 57: ......
Page 58: ......
Page 59: ......
Page 60: ......
Page 61: ......
Page 62: ......
Page 276: ......
Page 277: ......
Page 278: ......
Page 279: ......
Page 280: ......
Page 281: ......
Page 282: ......
Page 283: ......
Page 284: ......
Page 285: ......
Page 286: ......
Page 287: ......
Page 288: ......
Page 289: ......
Page 290: ......
Page 291: ......
Page 292: ......
Page 293: ......
Page 294: ......
Page 295: ......
Page 296: ......
Page 297: ......
Page 298: ......
Page 299: ......
Page 300: ......
Page 301: ......
Page 302: ......