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Assembler User Guide
Preface
Overview of the Assembler
Overview of the ARM Architecture
Structure of Assembly Language Modules
Writing ARM Assembly Language
Condition Codes
Using the Assembler
Symbols, Literals, Expressions, and Operators
Symbol naming rules
Variables
Numeric constants
Assembly time substitution of variables
Register-relative and PC-relative expressions
Labels
Labels for PC-relative addresses
Labels for register-relative addresses
Labels for absolute addresses
Numeric local labels
Syntax of numeric local labels
String expressions
String literals
Numeric expressions
Syntax of numeric literals
Syntax of floating-point literals
Logical expressions
Logical literals
Unary operators
Binary operators
Multiplicative operators
String manipulation operators
Shift operators
Addition, subtraction, and logical operators
Relational operators
Boolean operators
Operator precedence
Difference between operator precedence in assembly
VFP Programming
Assembler Command-line Options
ARM and Thumb Instructions
VFP Instructions
Directives Reference
Via File Syntax
Variables
| Non-Confidential |  PDF version | ARM DUI0379H | ||
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| Home > Symbols, Literals, Expressions, and Operators > Variables | ||||
7.2 Variables
You can declare numeric, logical, or string variables using assembler directives.
The value of a variable can be changed as assembly proceeds. Variables
are local to the assembler. This means that in the generated code
or data, every instance of the variable has a fixed value.
The type of a variable cannot be changed. Variables are one of the following types:
- Numeric.
- Logical.
- String.
The range of possible values of a numeric variable is the
same as the range of possible values of a numeric constant or numeric
expression.
The possible values of a logical variable are
{TRUE} or {FALSE}.The range of possible values of a string variable is the same
as the range of values of a string expression.
Use the
GBLA, GBLL, GBLS, LCLA, LCLL,
and LCLS directives to declare symbols representing variables,
and assign values to them using the SETA, SETL,
and SETS directives. Example
a SETA 100
L1 MOV R1, #(a*5) ; In the object file, this is MOV R1, #500
a SETA 200 ; Value of 'a' is 200 only after this point.
; The previous instruction is always MOV R1, #500
…
BNE L1 ; When the processor branches to L1, it executes
; MOV R1, #500Related concepts
| Non-Confidential | PDF version | ARM DUI0379H |
| Copyright © 2007, 2008, 2011, 2012, 2014-2016 ARM. All rights reserved. |
| Home > Symbols, Literals, Expressions, and Operators > Variables |
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