ARM Constant and Variable Declarations

9/7/2007

The following ARM Assembly directives are for setting constants.

Directive	Syntax	Description
*	label *expression	Identical to EQU. Gives a symbolic label to a fixed or program-relative expression.
CN	label CN numeric-expression	Names a coprocessor register number; c0 to c15 are predefined and cannot be used as labels.
CP	label CP numeric-expression	Gives a name to a coprocessor number, if available, that must be within the range 0 to 15. The names p0 - p15 are predefined and cannot be used as labels.
EQU	label EQU expression	Gives a symbolic label to a fixed or program-relative expression.
FN	label FN numeric-expression	Defines the names of floating-point registers, if available. The names F0-F7 and f0-f7 are predefined. The predefined register names cannot be used as labels but can be used as numeric expressions.
RN	label RN numeric-expression	Defines register names. Refer to registers by name only. The names R0-R15, r0-r15, PC, pc, LR, and lr are predefined. The predefined register names cannot be used as labels but can be used as numeric expressions.

The assembler supports global and local variables. The scope of global variables extends across the entire source file, while that of local variables is restricted to a particular instantiation of a macro.

The following table ARM assembly directives are for setting local and global variables.

Directive	Syntax	Description
GBLA	GBLA variable-name	Defines a global arithmetic variable. Values of arithmetic variables are 32-bit unsigned integers.
GBLL	GBLL variable-name	Defines a global logical variable.
GBLS	GBLS variable-name	Defines a global string variable.
LCLA	LCLA variable-name	Defines a local arithmetic variable with an initial state of 0.
LCLL	LCLL variable-name	Defines a local logical variable with an initial state of FALSE.
LCLS	LCLS variable-name	Defines a local string variable with an initial state of NULL string.
SETA	variable-name SETA expression	Sets the value of an arithmetic variable.
SETL	variable-name SETL expression	Sets the value of a logical variable.
SETS	variable-name SETS expression	Sets the value of a string variable.

Note that when you set the value of a string variable, you must use quotes.

You can declare local variables only from within a macro. In addition, after you declare a variable, you cannot use its name for any other purpose.

The assembler substitutes values for some variables:

• If a variable name has a $ character prefix, the assembler substitutes the variable value before it checks the line syntax.
• If the variable is a logical or arithmetic variable, the assembler performs an .STR operation on the variable, and replaces the variable with the result of the operation.

See Also

Concepts

ARM Assembler Directives