This document provides information about the Computer Organization and Architecture course for the 4th semester of the B.E. program at Laxmi Institute of Technology, Sarigam. It includes details about the course content which covers topics such as computer data representation, assembly language programming, CPU, and memory organization. The document then focuses on the topics of control memory, address sequencing, and microprogram examples. It provides explanations of control memory, the advantages of microprogrammed control, and the addressing capabilities required for control memory. Finally, it includes the format and coding for microinstructions along with examples.

1. Laxmi Institute of Technology, Sarigam
Academic Year - 2023-2024
COMPUTER SCIENCE AND ENGINEERING DEPARTMENT
CLASS: B.E, 2nd Year, Semester - 4th
Faculty Name: Ms. Sanchi Upadhyay
CSE Department
LIT, Sarigam
Subject: Computer Organization & Architecture
Subject Code: 3140707
Semester: IV

2. Subject: Computer Organization & Architecture
Subject Code: 3140707
Semester: IV
Teaching and Examination Scheme:

3. Subject Overview
Sr. No. Units
1 Computer Data Representation & Register Transfer and Micro-operations
2 Basic Computer Organization and Design
3 Assembly Language Programming
4 Microprogrammed Control Organization
5 Central Processing Unit
6 Pipeline And Vector Processing
7 Computer Arithmetic
8 Input-Output Organization
9 Memory Organization
10 Multiprocessors

4. ❏ Topics to be covered
➔ Control Memory
➔ Address sequencing
➔ Micro program example
➔ Design of Control Unit

5. ❏ Control Memory

6. ❏ Control Memory
➢ A computer that employs a microprogrammed control unit will have two separate
memories: a main memory and a control memory.
➢ The control memory holds a fixed microprogram that can not be altered by the
occasional user.
➢ The microprogram consists of microinstructions that specify various internal control
signals for execution of register microoperation.
➢ Microinstructions generates the microoperations to fetch instruction from main
memory; to evaluate the effective address, to execute the operation specified by the
instruction, and to return control to the fetch of next instruction.

7. ❏ Control Memory
The main Advantage of microprogrammed control is
➢ Different operations can be performed using a different control sequences and storing
different set of microinstructions in control memory
➢ It is not necessary to change the hardware or wiring
➢ Only the microprogram in the control memory is to be changed to perform different
operation

8. ❏ Address Sequencing
➢ Microinstructions are stored in control memory in groups, with each group specifying
a routine.
➢ The transformation from the instruction code bits to an address in control memory
where the routine is located is referred to as a mapping process.
➢ The address sequencing capabilities required in a control memory are:
1. Incrementing of the control address register.
2. Unconditional branch or conditional branch, depending on status bit conditions.
3. A mapping process from the bits of the instruction to an address for control memory.
4. A facility for subroutine call and return.

9. ❏ Address Sequencing

10. ❏ Microinstruction Code Format
➢ F1, F2, F3: Microoperation fields
➢ CD: Condition for branching
➢ BR: Branch field
➢ AD: Address field
F1 F2 F3 CD BR AD
3 3 3 2 2 7

11. ❏ Symbols & Binary Code for Microinstruction Fields
F1 Microoperation Symbol
000 None NOP
001 AC AC + DR ADD
010 AC 0 CLRAC
011 AC AC + 1 INCAC
100 AC DR DRTAC
101 AR DR(0-10) DRTAR
110 AR PC PCTAR
111 M[AR] DR WRITE
F2 Microoperation Symbol
000 None NOP
001 AC AC - DR SUB
010 AC AC DR OR
011 AC AC DR AND
100 DR M[AR] READ
101 DR AC ACTDR
110 DR DR + 1 INCDR
111 DR(0-10) PC PCTDR

12. ❏ Symbols & Binary Code for Microinstruction Fields
F3 Microoperation Symbol
000 None NOP
001 AC AC + DR XOR
010 AC AC’ COM
011 AC shl AC SHL
100 AC shr AC SHR
101 PC PC + 1 INCPC
110 PC AR ARTPC
111 Reserved
CD Symbol Comments
00 U - 1 Unconditional branch
01 I - DR(15) Indirect address bit
10 S - AC(15) Sign bit of AC
11 Z - AC = 0 Zero value in AC

13. ❏ Symbols & Binary Code for Microinstruction Fields
BR Symbol Function
00 JMP CAR AD if condition = 1, CAR CAR+1 if condition = 0
01 CALL CAR AD, SBR CAR+1 if condition=1, CAR CAR+1 if condition=0
10 RET CAR SBR (Return from subroutine)
11 MAP CAR(2-5) DR(11-14), CAR(0,1,6) 0

15. ❏ Question asked in GTU examination.
1 Draw and explain flow chart of address sequencing.
2 Draw and explain 20 bits microinstruction code format.
3 What is micro-programmed control architecture?
4 Explain Control Memory.
5 Difference between Hardwired and Micro-programmed control unit.
6 Write a note on micro program sequencer.
7 What is a micro operation? List and explain its categories.
8
Explain with help of diagram the working of basic computer, which uses
micro-programmed control.

16. Thank You!