Computer Architecture and Organization - Addressing Modes 3, Study notes of Computer Architecture and Organization

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Unit-1: Addressing Modes

 Recap

 Session Objectives & Teaching Learning

Material

 Session Plan

 Relative Addressing Mode

 Base register Addressing mode

 Indexed Addressing mode

 Stack Addressing mode

 Comparative analysis between various

addressing modes

 Assignment

 References

OutLine

 Session Objectives

◦ To provide knowledge on displacement

addressing mode that enable the students to

know the working model of control instructions,

segmentation problems and array references.

 Teaching Learning Material

◦ LCD, White board Marker, Presentation slides

Objectives & Teaching

Learning Material

Session Plan

Time (in min) Content

Learning Aid and Methodology

Faculty Approach

Typical Student Activity

Skill and Competency Developed

Re-Cap Quiz Presentation^ Questions Organizes^ Answers Identifies^ Knowledge Evaluation

Assembly Language programming

Explains Presentation Listens Application

Computation of

performance

factors

Explains

Presentatio n

Listens Analytical

10 Drawing graphs Explains

Presentatio n

Observes Synthesis

Conclusion and Summary Summary^ Facilitates^

Listens Participates

Comprehensio n

Base Register Addressing Mode

Opcode^ Opcode

Base-register addressing also exploits the locality if memory reference

 (^) Advantage:  (^) It us a convenient means if implementing segmentation.

 (^) Disadvantage:  (^) Complexity

 (^) It us a convenient means if implementing segmentation.

2’s Complement

2’s Complement

Main Memory

Operan d

Base Register

Base Register

E A

Indexed Addressing Mode

Opcode^ Opcode

For indexing the interpretation is typically the following: the address field reference a main memory address, and the referenced register contain a positive displacement from that address.  (^) Example:- A[1], a[2]

• (^) Base address of array A is added to the index value1 for EA

 (^) Advantage:  (^) Special Locality

Address^ Address

Main Memory

Operan d

Index Register

Index Register

E A

Comparisons Mode Algorithm Advantage Disadvantage 1 Implied Operand=ΦΦ No Memory references

Limited Computation capability 2 Immediat e

Operand=Φ1 No memory Reference

Limited operand magnitude

3. Direct EA =Φ A Simple Limited address space 4 Indirect EA =Φ(A) Large Address space Multiple Memory references
4. Register EA =Φ R No memory Reference

Limited address space

1

Register Indirect

EA =Φ (R ) Large address space Extra memory space

2

Relative EA =Φ PC+2’s Complement

Use for control instructions

Complexity

3

Base Register

EA=BA+ 2’s Complement

convenient during segmentation

Complexity

4

Indexed EA= A+ Index value

Accessing array elements Array lower bounds

7 Stack EA=Φ Top of Stack

No memory Reference

Limited Applicability

Displacement Addressing modes

 Relative Addressing Mode

 Base register Addressing mode

 Indexed Addressing mode

 Stack Addressing mode

 (^) Basic Addressing Modes differences

Summary

Text Book

 William Stallings “Computer Organization

and architecture” Prentice Hall, 7th edition,

References