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Lec 3

The document provides an overview of ARM Cortex-M assembly language, detailing basic data instructions, load/store instructions, and examples of translating C code into assembly. It explains the ARM architecture's data sizes, instruction sets, and various operations such as addition, subtraction, and logical shifts. Additionally, it includes examples of how to implement C assignments and conditional statements in ARM assembly language.

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Karem ahmed Labib mohamed
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42 views10 pages

Lec 3

The document provides an overview of ARM Cortex-M assembly language, detailing basic data instructions, load/store instructions, and examples of translating C code into assembly. It explains the ARM architecture's data sizes, instruction sets, and various operations such as addition, subtraction, and logical shifts. Additionally, it includes examples of how to implement C assignments and conditional statements in ARM assembly language.

Uploaded by

Karem ahmed Labib mohamed
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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ARM Cortex -

M Assembly
Language
ARM data instruction

• Basic format:
ADD R0,R1,R2 R0=R1+R2
- Computes R1+R2 , Stores in
R0.
• Immediate operand:
ADD R0,R1,#2 R0=R1+2
- Computes R1+R2, stores in
R0.
ARM data instruction
• ADD, ADC : add(w. carry)
• SUB, SBC : Subtract (w. carry)
• MUL : multiply
• AND , ORR, EOR
• BIC : bit clear Like AND
• LSL , LSR : logical shift left/right
• ROR : rotate right
Data Sizes and Instruction Sets

The ARM is a 32-bit architecture.

When used in relation to the ARM:

Byte means 8 bits

Halfword means 16 bits (two bytes)

Word means 32 bits (four bytes)

Most ARM’s implement two instruction sets

32-bit ARM Instruction Set


4

16-bit Thumb Instruction Set


ARM assembly language

• Outline
• The ARM programmers’ model
• The ARM instruction set
• Writing simple programs

5
ARM load/store instructions

• LDR, LDRH,LDRB : load (half- word, byte)


• STR, STRH, STRB : store (half- word, byte)
• Addressing modes:
- Register indirect : LDR R0, [R1]
- With constant : LDR R0 ,[R1,#4]
• Load from memory into a register
LDR R8,[R10]
• C:
Example: C X=(a+b)-c;
• Assembler:
assignments LDR R4,=4 ;get address for a
R4= address a
R0= value a
LDR R0,[R4] ;get value of a
LDR R4,=B ; get address for b , reusing r4 R4= address b
LDR R1,[R4] ; get value of b R1= value b
ADD R3,R0,R1 ; compute a+b R3=R0+R1=a+b
LDR R4,=C ; get address for c R4= address c
LDR R2,[R4] ; get value of c
R2= value c
SUB R3,R3,R2 ; complete computation of x
R3=R3-R2=a+b-c
LDR R4,=X ; get address for x
STR R3,[R4] ; store value of 1 R4= address x
R4=R3
Example: C assignments
• C:
y=a*(b+c);
• Assembler

MUL R2,R2,R0 ; Compute final value for y


LDR R4,=Y ; get address for y
STR R2, [R4] ; store y
Example: C assignments
• C:
Z= (A<<2) I (B&15);
• Assembler
Example: if statement
• C:
If (a>b) {x=5; y=c+d;} else x=c-d;
• Assembler

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