ARM VERSION 1.2 - Manual (Page 298)

Directives Reference
7-16 Copyright © 2000, 2001 ARM Limited. All rights reserved. ARM DUI 0068B
7.3.3 FIELD
The FIELD directive describes space within a storage map that has been defined using the
MAP directive. # is a synonym for FIELD .
Syntax
{label} FIELD expr
where:
label is an optional label. If specified, label is assigned the value of the storage
location counter, {VAR} . The storage location counter is then incremented
by the value of expr .
expr is an expression that evaluates to the number of bytes to increment the
storage counter.
Usage
If a storage map is set by a MAP directive that specifies a base-register, the base register
is implicit in all labels defined by following FIELD directives, until the next MAP directive.
These register-relative labels can be quoted in load and store instructions (see MAP on
page 7-15).
Note
You must be careful when using MAP , FIELD , and register-relative labels. See Describing
data structures with MAP and FIELD directives on page 2-51 for more information.
Example
The following example shows how register-relative labels are defined using the MAP and
FIELD directives.
MAP 0,r9 ; set {VAR} to the address stored in r9
FIELD 4 ; increment {VAR} by 4 bytes
Lab FIELD 4 ; set Lab to the address [r9 + 4]
; and then increment {VAR} by 4 bytes
LDR r0,Lab ; equivalent to LDR r0,[r9,#4]