Writing ARM and Thumb Assembly Language
ARM DUI 0068B Copyright © 2000, 2001 ARM Limited. All r ights reserved. 2-51
2.10 Describing data structures with MAP and FIELD directives
You can use the
MAP
and
FIELD
directives to describe dat a structures. The se directives are
always used together.
Data structures defined using
MAP
and
FIELD
:
•are easily maintainable
•can be used to describe multiple instances of the same structure
•make it easy to access data efficientl y.
The
MAP
directive specifies the base address of the data structure. Refe r to MAP on
page7-15 for further information.
The
FIELD
directive specifies the amount of memory required for a data item, and can
give the data item a label. It is repeated for each data item in the structure. Refer to
FIELD on page 7-16 for further information.
Note
No space in memory is allocated when a map is defined. Use define constant directives
(for example,
DCD
) to allocate space in memory.