CONTROL UNITTEAM 1:

Miguel Harmant

Rodney Rodriguez

Elias Crespo

Javier Parra

Alfredo Alonso

Marc-Wayne Anglin

WHAT IS A MICRO-INSTRUCTION?

WHAT ARE MICRO-OPERATIONS?

BASIC CONCEPTS

• Single instruction in a micro-program.

• Smaller series of steps that compose a micro-instruction.

• Atomic operation by the CPU.

BASIC MICRO-OPERATIONS

• Data transfers between registers.• Data Transfer from registers to memory• Data transfer from memory to registers• Logic and arithmetic operations.

BASIC COMPONENTS OF THE CPU

ALU - does the actual computation or processing of data.

Registers - set of internal memory. Internal Data paths (Bus) - need to

transfer data between the various registers and the ALU.

External Data paths - distribute data to other components.

CONTROL UNIT -controls the movement of data and instruction into and out of the CPU and controls the operation of the ALU.

CPU STRUCTURE

WHAT IS THE CONTROL UNIT ?

 Is the circuitry that controls the flow of information through the CPU.

 It coordinates the micro-operations of other units within it.

 In other words, it is the brain within the brain.

BASIC FUNCTIONS OF THE CU

Sequencing

Stepping through the micro-instructions.Maintaining proper sequence.

Execution

Interpreting input signals into output control signals.

Executes Control signals.

EXAMPLE OF THE CU OPERATIONS

FETCH-CYCLE Control signal Sequence

MAR <- (PC) Control unit activates

signal to open gates between PC and MAR 

MBR <- (memory) Open gates between

MAR and address bus Memory read control

signal Open gates between

data bus and MBR

 IR <- (MBR)  Open gates from MBR

to Instruction Register

BASIC ARCHITECTURE OF THE CONTROL UNIT

TYPES OF CONTROL UNIT

RISC architecture CISC architecture

Hard-wired

Designed as a combinatorial and sequential logic circuit.

Input logic signals are transformed into output logic signals, which are the control signals.

Faster.

Micro-programmed

The control signal values for each micro-operation are stored in memory.

Micro-operations that compose control signals are read from memory.

Simpler to modify and construct.

HARD-WIRED CONTROL UNIT BASIC DESIGN

EXAMPLE OF A BASIC COMPUTER HARD-WIRED IMPLEMENTATION

COMPONENTS DESCRIPTION

Instruction Decoder

 Takes the input from the op-code field of the instruction register and activates one of its 8 output lines.

 Each line corresponds to one of the instructions in the computer's instruction set.

Different Control Signals are produced depending on the op-code.

COMPONENTS DESCRIPTION (CONTINUED)

Ring Counter

Continuously cycles from t0 to t5.

CONTROL MATRIX

Control matrix

 It receives input from the ring counter and the instruction decoder and provides the proper sequence of control signals.

INSTRUCTION SET FOR THE BASIC COMPUTER

INSTRUCTION SET FOR THE BASIC COMPUTER(CONTINUED)

TIMING DIAGRAM

REVIEW QUESTIONS?1. What are the basic micro-operations?2. What are the three main components of

the CPU?3. What is the Control Unit?4. What are the two basic functions of the

Control Unit?5. What are the two types of Control Unit?6. How are they constructed?7. What is RISC and CISC?8. Which are the differences between the two

types of Control Unit?9. What are the advantages of each?10. What are the disadvantages of each?

END OF PRESENTATION