ARM VERSION 1.2 manual Making faster access possible, If you want the equivalent of the C code

Writing ARM and Thumb Assembly Language

Making faster access possible

To gain faster access to a section of memory:

1.Describe the memory section as a structure.

2.Use a register to address the structure.

For example, consider the definitions in Example 2-22.

Example 2-22

StartOfData	EQU	0x1000
EndOfData	EQU	0x2000
	MAP	StartOfData
Integer	FIELD	4
String	FIELD	MaxStrLen
Array	FIELD	ArrayLen*8
BitMask	FIELD	4
EndOfUsedData	FIELD	0
	ASSERT	EndOfUsedData <= EndOfData

If you want the equivalent of the C code:

Integer = 1;

String = "";

BitMask = 0xA000000A;

With the definitions from Example 2-22, the assembly language code can be as shown in Example 2-23.

Example 2-23

MOV	r0,#1
LDR	r1,=Integer
STR	r0,[r1]
MOV	r0,#0
LDR	r1,=String
STRB	r0,[r1]
MOV	r0,#0xA000000A
LDR	r1,=BitMask
STRB	r0,[r1]

Example 2-23 uses LDR pseudo-instructions. Refer to Loading with LDR Rd, =const on

page 2-27 for an explanation of these.

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