4.8.10 Substitution Symbols

Symbols can be assigned a string value. This enables you to create aliases for character strings by equating them to symbolic names. Symbols that represent character strings are called substitution symbols. When the assembler encounters a substitution symbol, its string value is substituted for the symbol name. Unlike symbolic constants, substitution symbols can be redefined.

A string can be assigned to a substitution symbol anywhere within a program; for example:

.global _table .asg "B14", PAGEPTR .asg "*+B15(4)", LOCAL1 .asg "*+B15(8)", LOCAL2 LDW *+PAGEPTR(_table),A0 NOP 4 STW A0,LOCAL1

When you are using macros, substitution symbols are important because macro parameters are actually substitution symbols that are assigned a macro argument. The following code shows how substitution symbols are used in macros:

MAC .macro src1, src2, dst ; Multiply/Accumulate macro MPY src1, src2, src2 NOP ADD src2, dst, dst .endm * MAC macro invocation MAC A0,A1,A2

See Section 6 for more information about macros.