Assembler control directives

In this section:

Syntax

$filename

/* comment */

// comment

CASEOFF

CASEON

INCLUDE filename

LTORG

RADIX expr

Parameters

`comment`	Comment ignored by the assembler.
`expr`	Default base—default 10 (decimal).
`filename`	Name of file to be included. The `$` character must be the first character on the line.

Description

These directives provide control over the operation of the assembler. For information about the restrictions that apply when using a directive in an expression, see Expression restrictions.

Directive	Description	Expression restrictions
`$`	Includes a file.
`/comment/`	C-style comment delimiter.
`//`	C++ style comment delimiter.
`CASEOFF`	Disables case sensitivity.
`CASEON`	Enables case sensitivity.
`INCLUDE`	Includes a file.
`LTORG`	Directs the current literal pool to be assembled immediately after the directive.
`RADIX`	Sets the default base on all numeric values.	No forward references No external references Absolute Fixed

Table 155. Assembler control directives

Use $ to insert the contents of a file into the source file at a specified point. $filename is an alias for #include "filename", see the section Including source files under C-style preprocessor directives. The $ character must be the first character on the line.

Use /*...*/ to comment sections of the assembler listing.

Use // to mark the rest of the line as comment.

Use INCLUDE to insert the contents of a file into the source file at a specified point. INCLUDE filename is an alias for #include <filename>, see the section Including source files under C-style preprocessor directives. Note that INCLUDE only searches in the system header directories.

Use LTORG to direct where the current literal pool is to be assembled. By default, this is performed at every END and RSEG directive. For an example, see LDR (ARM).

Use RADIX to set the default base for constants. The default base is 10.

Controlling case sensitivity

Use CASEON or CASEOFF to turn case sensitivity on or off for user-defined symbols. By default, case sensitivity is off.

When CASEOFF is active all symbols are stored in upper case, and all symbols used by ilink should be written in upper case in the ilink definition file.

When CASEOFF is set, label and LABEL are identical in this example:

            module  caseSensitivity1
            section  MYCODE:CODE(2)

            caseoff
label       nop                 ; Stored as "LABEL".
            b       LABEL
            end

The following will generate a duplicate label error:

            module  caseSensitivity2

            caseoff
label       nop                 ; Stored as "LABEL".
LABEL       nop                 ; Error, "LABEL" already defined.
            end

Including a source file

This example uses $ to include a file defining macros into the source file. For example, these macros could be defined in Macros.inc:

; Exchange registers a and b.
; Use register c for temporary storage.

xch         macro   a,b,c
            movs    c,a
            movs    a,b
            movs    b,c
            endm

The macro definitions can be included with a $ directive, as in:

            name    includeFile
            section MYCODE:CODE(2)

; Standard macro definitions.
$Macros.inc

xchRegs     xch     r0,r1,r2
            bx      lr

            end

Defining comments

This example shows how /*...*/ can be used for a multi-line comment:

/*
Program to read serial input.
Version 1: 19.2.11
Author: mjp
*/

See also the section Comments in C-style preprocessor directives under C-style preprocessor directives.

Changing the base

To set the default base to 16:

            module  radix
            section MYCODE:CODE(2)

            radix   16            ; With the default base set
            movs    r0,#12        ; to 16, the immediate value
            ;...                  ; of the mov instruction is
                                  ; interpreted as 0x12.

; To reset the base from 16 to 10 again, the argument must be
; written in hexadecimal format.

            radix   0x0a          ; Reset the default base to 10.
            movs    r0,#12        ; Now, the immediate value of
            ;...                  ; the mov instruction is
                                  ; interpreted as 0x0c.
            end

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