The document discusses micro-programmed control units. It begins with an introduction that defines the control unit as the engine that runs the computer by performing sequencing and execution with control signals. It then describes the block diagram and sources of control signals like the clock and instruction register. The types of control units are discussed as being either hardwired or micro-programmed, with the latter storing control signals in a control memory. Micro-programmed control units are more flexible but slower. Advantages are that the design is less complex, more flexible for modifications, and faults can be more easily diagnosed.

1. G. H RAISONI COLLEGE OF
ENGINEERING AND MANAGMENT, PUNE
(AN AUTONOMOUS INSTITUTE & AFFILIATED TO PUNE UNIVERSITY)
TAE – 01
Subject – Computer Architeacture & Organization
Topic – Micro-programmed Control Unit
Guided by - Mis. Kavita joshi (mam)
Name – 1] Abhishek R Chambhare { SECA15 }
Department of Electronic & Telecommunication Engineering

2. CONTENT :-
 Introduction
 Block Diagram of Control unit
 Control Signals Sources
 Control Signals Output
 Types
 Comparison
 Control Unit Faction
 Advantage of Control Unit

3. INTRODUCTION :-
 Control Unit is the engine that runs the entire computer
with the help of the control signals.
 It perform the correct sequencing of the correct signals.
 It controls everything with a few control signals that
points within processor and a few control signals to the
system bus
 All the micro-operation are controlled by CU by
performing two basic tasks :-
Sequencing: It causes the processor to step through the
series of micro-operation in proper sequence, based on
program being executed.
Execution: It causes each micro-operation to be performed.

4. BLOCK DIAGRAM OF CONTROL UNIT :-

5. CONTROL SIGNAL SOURCES :-
 Clock :-
It helps to synchronize the operation. It causes one micro-
operation to be performed for each clock pulse.
 Instruction Register :-
Op-code for current instruction.
Determines which micro-instructions are performed.
 Flags :-
State of CPU
Results of previous operations
 From Control Bus :-
Interrupts / Bus Requests
Acknowledgements

6. CONTROL SIGNAL OUTPUTS :-
 Within Processor :-
Cause data movement.
Activate specific functions.
 Via Main Bus :-
To memory.
To I/O modules.

7. TYPES :-
 There are two design approach for Control unit :-
1] Hardwired approach :-
 Hardwired Control Unit is a unit that uses combinational
logic units, featuring a finite number of gates that can
generate specific results based on the instructions that were
used to invoke those responses.
 Micro-programmed Control Unit is a unit that contains
microinstructions in the control memory to produce control
signals.
2] Micro-programming approach:-
 Micro-programmed Control Unit – The control signals
associated with operations are stored in special memory
units inaccessible by the programmer as Control Words.
 Control signals are generated by a program are similar to
machine language programs.

8. COMPARISON :-
Attributes Hardwired Control Micro-programming
Control
Speed Fast Slow
Cost of
Implementation
More Cheaper
Flexibility Difficult to modify Flexible
Ability to handle
complex instruction
Difficult Easier
Decoding Complex Easy
Application RISC CISC
Instruction Set Size Small Large
Control Memory Large Large

9. CONTROL UNIT FUNCTION :-
 Sequence login unit issues read command.
 Word specified in control address register is read into
control buffer register.
 Control buffer register contents generates control
signals and next address information.
 Sequence login loads new address into control buffer
register based on next address information from
control buffer register and ALU flags.

10. ADVANTAGE OF MICRO-PROGRAMMED CONTROL UNIT :-
 The design of micro-programmed control unit is less
complex because micro-programs are implemented sing
software routine.
 The micro-programmed control unit is more flexible
because design modification ,correction and
enhancement is easily possible.
 The new or modified instruction set of CPU can be easily
implemented by simple rewriting or modifying the
contents of control memory.
 The fault can be easily diagnosed in the micro- program
control unit using diagnostic tools by maintaining the
contents of flag’s ,register and counters.

11. THANK YOU