Assembler directives	described in Section 5
	Macro directives	described in Section 6
	Assembly language instructions	described in the TMS470R1x User's Guide.

armclinput file [options]

armcl	is the command that invokes the assembler through the compiler. The compiler considers any file with an .asm extension to be an assembly file and invokes the assembler.
input file	names the assembly language source file.
options	identify the assembler options that you want to use. Options are case sensitive and can appear anywhere on the command line following the command. Precede each option with one or two hyphens as shown.

Table 4-1 ARM Assembler Options

Option	Alias	Description
--absolute_listing	-aa	Creates an absolute listing. When you use --absolute_listing, the assembler does not produce an object file. The --absolute_listing option is used in conjunction with the absolute lister.
--asm_define=name[=def]	-ad	Sets the name symbol. This is equivalent to defining name with a .set directive in the case of a numeric value or with an .asg directive otherwise. If value is omitted, the symbol is set to 1. See Section 4.8.5.
--asm_dependency	-apd	Performs preprocessing for assembly files, but instead of writing preprocessed output, writes a list of dependency lines suitable for input to a standard make utility. The list is written to a file with the same name as the source file but with a .ppa extension.
--asm_includes	-api	Performs preprocessing for assembly files, but instead of writing preprocessed output, writes a list of files included with the .include directive. The list is written to a file with the same name as the source file but with a .ppa extension.
--asm_listing	-al	Produces a listing file with the same name as the input file with a .lst extension.
--asm_listing_cross_reference	-ax	Produces a cross-reference table and appends it to the end of the listing file; it also adds cross-reference information to the object file for use by the cross-reference utility. If you do not request a listing file but use the --asm_listing_cross_reference option, the assembler creates a listing file automatically, naming it with the same name as the input file with a .lst extension.
--asm_undefine=name	-au	Undefines the predefined constant name, which overrides any --asm_define options for the specified constant.
--cmd_file=filename	-@	Appends the contents of a file to the command line. You can use this option to avoid limitations on command line length imposed by the host operating system. Use an asterisk or a semicolon (* or ;) at the beginning of a line in the command file to include comments. Comments that begin in any other column must begin with a semicolon. Within the command file, filenames or option parameters containing embedded spaces or hyphens must be surrounded with quotation marks. For example: "this-file.asm"
--code_state={16|32}	-mt	--code_state=16 (or -mt) instructs the assembler to begin assembling instructions as 16-bit instructions; UAL syntax (.thumb) for ARMv7 and non-UAL syntax (.state16) otherwise. By default, the assembler begins assembling 32-bit instructions. You can reset the default behavior by specifying --code_state=32. For information on indirect calls in 16-bit versus 32-bit code, see the ARM Optimizing C/C++ Compiler User's Guide.
--endian	-me	Produces object code in little-endian format. For more information, see the ARM Optimizing C/C++ Compiler User's Guide.
--include_file=filename	-ahi	Includes the specified file for the assembly module. The file is included before source file statements. The included file does not appear in the assembly listing files.
--include_path=pathname	-I	Specifies a directory where the assembler can find files named by the .copy, .include, or .mlib directives. There is no limit to the number of directories you can specify in this manner; each pathname must be preceded by the --include_path option. See Section 4.5.1.
--quiet	-q	Suppresses the banner and progress information (assembler runs in quiet mode).
--symdebug:dwarf or --symdebug:none	-g	(DWARF is on by default) Enables assembler source debugging in the C source debugger. Line information is output to the object module for every line of source in the assembly language source file. You cannot use this option on assembly code that contains .line directives. See Section 4.13.

.copy ["]filename["] .include ["]filename["] .mlib ["]filename["]

4.5.1 Using the --include_path Assembler Option

The --include_path assembler option names an alternate directory that contains copy/include files or macro libraries. The format of the --include_path option is as follows:

There is no limit to the number of --include_path options per invocation; each --include_path option names one pathname. In assembly source, you can use the .copy, .include, or .mlib directive without specifying path information. If the assembler does not find the file in the directory that contains the current source file, it searches the paths designated by the --include_path options.

For example, assume that a file called source.asm is in the current directory; source.asm contains the following directive statement:

.copy "copy.asm"

Assume the following paths for the copy.asm file:

You could set up the search path with the commands shown below:

The assembler first searches for copy.asm in the current directory because source.asm is in the current directory. Then the assembler searches in the directory named with the --include_path option.

4.5.2 Using the TI_ARM_A_DIR Environment Variable

An environment variable is a system symbol that you define and assign a string to. The assembler uses the TI_ARM_C_DIR environment variable to name alternate directories that contain copy/include files or macro libraries.

The assembler looks for the TI_ARM_A_DIR environment variable and then reads and processes it. If the assembler does not find the TI_ARM_A_DIR variable, it then searches for TI_ARM_C_DIR. The processor-specific variables are useful when you are using Texas Instruments tools for different processors at the same time.

See the ARM Optimizing C/C++ Compiler User's Guide for details on TI_ARM_C_DIR.

NOTE

The TI_ARM_C_DIR environment variable takes precedence over the older TMS470_C_DIR environment variable if both are defined. If only TMS470_C_DIR is set, it will continue to be used. Likewise, the TI_ARM_A_DIR environment variable takes precedence over the older TMS470_A_DIR environment variable if both are defined. If only TMS470_A_DIR is set, it will continue to be used.

The command syntax for assigning the environment variable is as follows:

The pathnames are directories that contain copy/include files or macro libraries. The pathnames must follow these constraints:

• Pathnames must be separated with a semicolon.
• Spaces or tabs at the beginning or end of a path are ignored. For example the space before and after the semicolon in the following is ignored:
set TI_ARM_A_DIR= c:\path\one\to\tools ; c:\path\two\to\tools
• Spaces and tabs are allowed within paths to accommodate Windows directories that contain spaces. For example, the pathnames in the following are valid:

In assembly source, you can use the .copy, .include, or .mlib directive without specifying path information. If the assembler does not find the file in the directory that contains the current source file or in directories named by the --include_path option, it searches the paths named by the environment variable.

For example, assume that a file called source.asm contains these statements:

.copy "copy1.asm" .copy "copy2.asm"

Assume the following paths for the files:

You could set up the search path with the commands shown below:

The assembler first searches for copy1.asm and copy2.asm in the current directory because source.asm is in the current directory. Then the assembler searches in the directory named with the --include_path option and finds copy1.asm. Finally, the assembler searches the directory named with TI_ARM_A_DIR and finds copy2.asm.

The environment variable remains set until you reboot the system or reset the variable by entering one of these commands:

[label[:]]mnemonic [operand list][;comment]

4.6.1 Label Field

A label must be a legal identifier (see Section 4.8.1) placed in column 1. Every instruction may optionally have a label. Many directives allow a label, and some require a label.

A label can be followed by a colon (:). The colon is not treated as part of the label name. If you do not use a label, the first character position must contain a blank, a semicolon, or an asterisk.

When you use a label on an assembly instruction or data directive, an assembler symbol (Section 4.8) with the same name is created. Its value is the current value of the section program counter (SPC, see Section 2.4.5). This symbol represents the address of that instruction. In the following example, the .word directive is used to create an array of 3 words. Because a label was used, the assembly symbol Start refers to the first word, and the symbol will have the value 40h.

. . . . 9 * Assume some code was assembled 10 00000040 0000000A Start: .word 0Ah,3,7 00000044 00000003 00000048 00000007

A label on a line by itself is a valid statement. When a label appears on a line by itself, it points to the instruction on the next line (the SPC is not incremented):

1 00000000 Here: 2 00000000 00000003 .word 3

A label on a line by itself is equivalent to writing:

Here: .equ $ ; $ provides the current value of the SPC

If you do not use a label, the character in column 1 must be a blank, an asterisk, or a semicolon.

4.6.2 Mnemonic Field

The mnemonic field follows the label field. The mnemonic field cannot start in column 1; if it does, it is interpreted as a label. There is one exception: the parallel bars (||) of the mnemonic field can start in column 1. The mnemonic field contains one of the following items:

• Machine-instruction mnemonic (such as ADD, MUL, STR)
• Assembler directive (such as .data, .list, .equ)
• Macro directive (such as .macro, .var, .mexit)
• Macro invocation

4.6.3 Operand Field

The operand field follows the mnemonic field and contains zero or more comma-separated operands. An operand can be one of the following:

• an immediate operand (usually a constant or symbol) (see Section 4.7 and Section 4.8)
• a register operand
• a memory reference operand
• an expression that evaluates to one of the above (see Section 4.9)

An immediate operand is encoded directly in the instruction. The value of an immediate operand must be a constant expression. Most instructions with an immediate operand require an absolute constant expression, such as 1234. Some instructions (such as a call instruction) allow a relocatable constant expression, such as a symbol defined in another file. (See Section 4.9 for details about types of expressions.)

A register operand is a special pre-defined symbol that represents a CPU register.

A memory reference operand uses one of several memory addressing modes to refer to a location in memory. Memory reference operands use a special target-specific syntax defined in the appropriate CPU and Instruction Set Reference Guide.

You must separate operands with commas. Not all operand types are supported for all operands. See the description of the specific instruction in the CPU and Instruction Set Reference Guide for your device family.

4.6.4 Comment Field

A comment can begin in any column and extends to the end of the source line. A comment can contain any ASCII character, including blanks. Comments are printed in the assembly source listing, but they do not affect the assembly.

A source statement that contains only a comment is valid. If it begins in column 1, it can start with a semicolon ( ; ) or an asterisk ( *). Comments that begin anywhere else on the line must begin with a semicolon. The asterisk identifies a comment only if it appears in column 1.

4.7.1 Integer Literals

The assembler maintains each integer literal internally as a 32-bit signless quantity. Literals are considered unsigned values, and are not sign extended. For example, the literal 00FFh is equal to 00FF (base 16) or 255 (base 10); it does not equal -1. which is 0FFFFFFFFh (base 16). Note that if you store 0FFh in a .byte location, the bits will be exactly the same as if you had stored -1. It is up to the reader of that location to interpret the signedness of the bits.

4.7.2 Character String Literals

A character string is a sequence of characters enclosed in double quotes. Double quotes that are part of character strings are represented by two consecutive double quotes. The maximum length of a string varies and is defined for each directive that requires a character string. Characters are represented internally as 8-bit ASCII characters.

These are examples of valid character strings:

Character strings are used for the following:

• Filenames, as in .copy "filename"
• Section names, as in .sect "section name"
• Data initialization directives, as in .byte "charstring"
• Operands of .string directives

4.7.3 Floating-Point Literals

A floating-point literal is a string of decimal digits followed by a required decimal point, an optional fractional portion, and an optional exponent portion. The syntax for a floating-point number is:

Replace nnn with a string of decimal digits. You can precede nnn with a + or a -. You must specify a decimal point. For example, 3.e5 is valid, but 3e5 is not valid. The exponent indicates a power of 10. These are examples of valid floating-point literals:

3.0 3.14 3. -0.314e13 +314.59e-2

The assembler syntax does not support all C89-style float literals nor C99-style hexadecimal constants, but the $$strtod built-in mathematical function supports both. If you want to specify a floating-point literal using one of those formats, use $$strtod. For example:

$$strtod(".3") $$strtod("0x1.234p-5")

You cannot directly use NaN, Inf, or -Inf as floating-point literals. Instead, use $$strtod to express these values. The "NaN" and "Inf" strings are handled case-insensitively. See Section 4.10.1 for built-in functions.

$$strtod("NaN") $$strtod("Inf")

4.8.1 Identifiers

Identifiers are names used as labels, registers, symbols, and substitution symbols. An identifier is a string of alphanumeric characters, the dollar sign, and underscores (A-Z, a-z, 0-9, $, and _). The first character in an identifier cannot be a number, and identifiers cannot contain embedded blanks. The identifiers you define are case sensitive; for example, the assembler recognizes ABC, Abc, and abc as three distinct identifiers.

4.8.2 Labels

An identifier used as a label becomes an assembler symbol, which represent an address in the program. Labels within a file must be unique.

NOTE

A mnemonic cannot begin in column 1 or it will be interpreted as a label. Mnemonic opcodes and assembler directive names without the . prefix are valid label names. Remember to always use whitespace before the mnemonic, or the assembler will think the identifier is a new label definition.

Symbols derived from labels can also be used as the operands of .bss, .global, .ref, or .def directives.

4.8.3 Local Labels

Local labels are especially useful in macros. If a macro contains a normal label and is called more than once, the assembler issues a multiple-definition error. If you use a local label and .newblock within a macro, however, the local label is used and reset each time the macro is expanded.

Up to ten local labels of the $n form can be in effect at one time. Local labels of the form name? are not limited. After you undefine a local label, you can define it and use it again. Local labels do not appear in the object code symbol table.

For more information about using labels in macros see Section 6.6.

4.8.4 Symbolic Constants

A symbolic constant is a symbol with a value that is an absolute constant expression (see Section 4.9). By using symbolic constants, you can assign meaningful names to constant expressions. The .set and .struct/.tag/.endstruct directives enable you to set symbolic constants (see Define Assembly-Time Constant). Once defined, symbolic constants cannot be redefined.

If you use the .set directive to assign a value to a symbol , the symbol becomes a symbolic constant and may be used where a constant expression is expected. For example:

shift3 .set 3 MOV R0, #shift3

You can also use the .set directive to assign symbolic constants for other symbols, such as register names. In this case, the symbolic constant becomes a synonym for the register:

AuxR1 .set R1 LDR AuxR1, [SP]

The following example shows how the .set directive can be used with the .struct, .tag. and .endstruct directives. It creates the symbolic constants K, maxbuf, item, value, delta, and i_len.

K .set 1024 ;constant definitions maxbuf .set 2*K 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 many predefined symbolic constants; these are discussed in Section 4.8.6.

4.8.5 Defining Symbolic Constants (--asm_define Option)

The --asm_define option equates a constant value or a string with a symbol. The symbol can then be used in place of a value in assembly source. The format of the --asm_define option is as follows:

The name is the name of the symbol you want to define. The value is the constant or string value you want to assign to the symbol. If the value is omitted, the symbol is set to 1. If you want to define a quoted string and keep the quotation marks, do one of the following:

• For Windows, use --asm_define=name="\"value\"". For example, --asm_define=car="\"sedan\""
• For UNIX, use --asm_define=name='"value"'. For example, --asm_define=car='"sedan"'
• For Code Composer, enter the definition in a file and include that file with the --cmd_file (or -@) option.

Once you have defined the name with the --asm_define option, the symbol can be used with assembly directives and instructions as if it had been defined with the .set directive. For example, on the command line you enter:

armcl --asm_define=SYM1=1 --asm_define=SYM2=2 --asm_define=SYM3=3 --asm_define=SYM4=4 value.asm

Since you have assigned values to SYM1, SYM2, SYM3, and SYM4, you can use them in source code. Example 4-2 shows how the value.asm file uses these symbols without defining them explicitly.

Within assembler source, you can test the symbol defined with the --asm_define option with these directives:

The argument to the $$isdefed built-in function must be enclosed in quotes. The quotes cause the argument to be interpreted literally rather than as a substitution symbol.

4.8.6 Predefined Symbolic Constants

The assembler has several types of predefined symbols.

$, the dollar-sign character, represents the current value of the section program counter (SPC).

In addition, the following predefined processor symbolic constants are available:

4.8.7 Registers

In addition, control register names are predefined symbols.

The names of ARM registers and their aliases are register symbols, including:

• Coprocessor registers, including C0-C15.
• Coprocessor IDs, including P0-P15.
• VFP registers, including D0-D31, S0-S31.
• NEON registers, including D0-D31, Q0-Q15.

Register symbols and aliases can be entered as all uppercase or all lowercase characters. For example, R13 could also be entered as r13, SP, or sp.

Control register symbols can be entered in all upper-case or all lower-case characters.

See the "Register Conventions" section of the ARM Optimizing C/C++ Compiler User's Guide for details about the registers and their uses.

Status registers can be entered as all uppercase or all lowercase characters; that is, CPSR could also be entered as cpsr, CPSR_ALL, or cpsr_all.

4.8.8 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:

.asg "SP", stack-pointer ; Assigns the string SP to the substitution symbol stack-pointer. .asg "#0x20", block2 ; Assigns the string #0x20 to the substitution symbol block2. ADD stack-pointer, stack-pointer, block2 ; Adds the value in SP to #0x20 and stores the result in SP.

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:

addl .macro dest, src ; addl macro definition ADDS dest, dest, src ; Add the value in register dest to the value in register src, ; and store the result in src. BLCS reset_ctr ; Handle overflow. .endm *addl invocation addl R4, R5 ; Calls the macro addl and substitutes R4 for dest and R5 for src. ; The macro adds the value of R4 and the value of R5, stores the ; result in R4, and handles overflow.

See Section 6 for more information about macros.

4.9.1 Mathematical and Logical Operators

The operands of a mathematical or logical operator must be well-defined expressions. That is, you must use the correct number of operands and the operation must make sense. For example, you cannot take the XOR of a floating-point value. In addition, well-defined expressions contain only symbols or assembly-time constants that have been defined before they occur in the directive's expression.

Three main factors influence the order of expression evaluation:

Table 4-5 lists the operators that can be used in expressions, according to precedence group.

The assembler checks for overflow and underflow conditions when arithmetic operations are performed during assembly. It issues a warning (the "value truncated" message) whenever an overflow or underflow occurs. The assembler does not check for overflow or underflow in multiplication.

4.9.2 Relational Operators and Conditional Expressions

The assembler supports relational operators that can be used in any expression; they are especially useful for conditional assembly. Relational operators include the following:

Conditional expressions evaluate to 1 if true and 0 if false and can be used only on operands of equivalent types; for example, absolute value compared to absolute value, but not absolute value compared to relocatable value.

4.9.3 Well-Defined Expressions

Some assembler directives, such as .if, require well-defined absolute constant expressions as operands. Well-defined expressions contain only symbols or assembly-time constants that have been defined before they occur in the directive's expression. In addition, they must use the correct number of operands and the operation must make sense. The evaluation of a well-defined expression must be unambiguous.

This is an example of a well-defined expression:

1000h+X

where X was previously defined as an absolute symbol.

4.9.4 Relocatable Symbols and Legal Expressions

All legal expressions can be reduced to one of two forms:

relocatable symbol ± absolute symbol

or

absolute value

Unary operators can be applied only to absolute values; they cannot be applied to relocatable symbols. Expressions that cannot be reduced to contain only one relocatable symbol are illegal.

Table 4-6 summarizes valid operations on absolute, relocatable, and external symbols. An expression cannot contain multiplication or division by a relocatable or external symbol. An expression cannot contain unresolved symbols that are relocatable to other sections.

Symbols that have been defined as global with the .global directive can also be used in expressions; in Table 4-6, these symbols are referred to as external.

4.9.5 Expression Examples

Following are examples of expressions that use relocatable and absolute symbols. These examples use four symbols that are defined in the same section:

.global extern_1 ; Defined in an external module intern_1: .word '"D' ; Relocatable, defined in current ; module LAB1: .set 2 ; LAB1 = 2 intern_2 ; Relocatable, defined in current ; module intern_3 ; Relocatable, defined in current ; module

• Example 1

The statements in this example use an absolute symbol, LAB1, which is defined to have a value of 2. The first statement loads the value 51 into R0. The second statement loads the value 27 into R0.

MOV R0, #LAB1 + ((4+3) * 7) ; R0 = 51 ; 2 + ((7) * 7) ; 2 + (49) = 51 MOV R0, #LAB1 + 4 + (3*7) ; R0 = 27 ; 2 + 4 + (21) = 27
• Example 2

The first statement in the following example is valid; the statements that follow it are invalid.

LDR R1, intern_1 - 10 ; Legal LDR R1, 10-intern_1 ; Can't negate reloc. symbol LDR R1, -(intern_1) ; Can't negate reloc. symbol LDR R1, intern_1/10 ; / isn't additive operator LDR R1, intern_1 + intern_2 ; Multiple relocatables
• Example 3

The first statement below is legal; although intern_1 and intern_2 are relocatable, their difference is absolute because they are in the same section. Subtracting one relocatable symbol from another reduces the expression to relocatable symbol + absolute value. The second statement is illegal because the sum of two relocatable symbols is not an absolute value.

LDR R1, intern_1 - intern_2 + intern_3 ; Legal LDR R1, intern_1 + intern_2 + intern_3 ; Illegal
• Example 4

A relocatable symbol's placement in the expression is important to expression evaluation. Although the statement below is similar to the first statement in the previous example, it is illegal because of left-to-right operator precedence; the assembler attempts to add intern_1 to extern_3.

LDR R1, intern_1 + intern_3 - intern_2 ; Illegal

4.10.1 Built-In Math and Trigonometric Functions

The assembler supports built-in functions for conversions and various math computations. Table 4-7 describes the built-in functions. The expr must be a constant value.

	!	undefined external reference
	'	.text relocatable
	+	.sect relocatable
	"	.data relocatable
	-	.bss, .usect relocatable
	%	relocation expression

$filename:starting source line:ending source line$

Label	column contains each symbol that was defined or referenced during the assembly.
Value	column contains an 8-digit hexadecimal number (which is the value assigned to the symbol) or a name that describes the symbol's attributes. A value may also be preceded by a character that describes the symbol's attributes. Table 4-8 lists these characters and names.
Definition	(DEFN) column contains the statement number that defines the symbol. This column is blank for undefined symbols.
Reference	(REF) column lists the line numbers of statements that reference the symbol. A blank in this column indicates that the symbol was never used.

Table 4-8 Symbol Attributes

	Character or Name	Meaning
	REF	External reference (global symbol)
	UNDF	Undefined
	'	Symbol defined in a .text section
	"	Symbol defined in a .data section
	+	Symbol defined in a .sect section
	-	Symbol defined in a .bss or .usect section