15.20 DCI

The DCI directive allocates two or four-byte aligned memory and defines the initial runtime contents of the memory.

Syntax

{label} DCI{.W} expr{,expr}

where:

expr

is a numeric expression.

.W

if present, indicates that four bytes must be inserted in Thumb code.

Usage

The DCI directive is very like the DCD or DCW directives, but the location is marked as code instead of data. Use DCI when writing macros for new instructions not supported by the version of the assembler you are using.

In ARM code, DCI allocates one or more words of memory, aligned on four-byte boundaries. It inserts up to three bytes of padding before the first defined word, if necessary, to achieve four-byte alignment.

In Thumb code, DCI allocates one or more halfwords of memory, aligned on two-byte boundaries. It inserts an initial byte of padding, if necessary, to achieve two-byte alignment.

You can use DCI to insert a bit pattern into the instruction stream. For example, use:

    DCI 0x46c0

to insert the Thumb operation MOV r8,r8.

Example macro

    MACRO           ; this macro translates newinstr Rd,Rm
                    ; to the appropriate machine code
    newinst     $Rd,$Rm
    DCI         0xe16f0f10 :OR: ($Rd:SHL:12) :OR: $Rm
    MEND

32-bit Thumb example

    DCI.W   0xf3af8000   ; inserts 32-bit NOP, 2-byte aligned.
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