Chapter 1 - Processor Components (1.1)

Question 1

What components does the CPU contain? (10)

Answer 1

1. Control Unit
2. Control Bus
3. Data Bus
4. Address Bus
5. Arithmetic Logic Unit
6. Accumulator
7. Program Counter
8. Current Instruction Register
9. Memory Address Register
10. Memory Data Register

Question 2

What does the Control Unit do?

Answer 2

Controls and coordinates activities of CPU and Fetch Decode Execute cycle, also contains the clock

Question 3

What is the Control Bus?

Answer 3

transmits control signals and provides status info between system components, coordinates the use of the data and address buses

Question 4

Is the control bus bi-directional?

Answer 4

Yes

Question 5

Give examples of the control lines from the control bus. (6)

Answer 5

1. Bus Request
2. Bus Grant
3. Memory Write
4. Memory Read
5. Interrupt Request
6. Clock

Question 6

What is a Bus Request?

Answer 6

indicates device is requesting use of data bus

Question 7

What is a Bus Grant?

Answer 7

indicates CPU granted access to data bus

Question 8

What is a Memory Write?

Answer 8

causes data on data bus to be written into addressed location

Question 9

What is a Memory Read?

Answer 9

causes data from addressed location to be placed on data bus

Question 10

What is an Interrupt Request?

Answer 10

indicates device is requesting access to CPU

Question 11

What is a Clock?

Answer 11

synchronises operations

Question 12

What is the Data Bus?

Answer 12

transmits data and instructions between system components

Question 13

Is the Data Bus bi-directional?

Answer 13

Yes

Question 14

What is the Address Bus?

Answer 14

transmits memory addresses specifying where data is to be sent to or retrieved from so that data is received and sent back to processor

Question 15

Is the address bus bi-directional?

Answer 15

No

Question 16

What is the Arithmetic Logic Unit?

Answer 16

Performs arithmetic and logic operations on data

Question 17

Give examples of what the Arithmetic Logic Unit can do. (6)

Answer 17

1. Adding
2. Subtracting
3. Multiplying,
4. Dividing
5. Comparing
6. Boolean (AND, OR, NOT)

Question 18

What is a Register?

Answer 18

Small but fast piece of memory which holds info for CPU to work

Question 19

What is the Accumulator?

Answer 19

Holds results of operations carried out

Question 20

What is the Program Counter?

Answer 20

Holds address of next instruction to be executed

Question 21

What is the Current Instruction Register?

Answer 21

Holds current instruction being executed and divides it into operand and opcode

Question 22

What is the Memory Address Register?

Answer 22

holds address of memory location that is to be read/written to.

Question 23

What is the Memory Data Register?

Answer 23

stores data read from or written to memory (also known as memory buffer register)

Question 24

State the Fetch phase of the Fetch Decode Execute Cycle. (3)

Answer 24

1. address from next instruction copied from program counter to memory address register
2. instruction held at MAR is copied to memory data register via data bus, simultaneously contents of PC is incremented so it holds address of next instruction
3. contents of MDR copied to current instruction register

Question 25

State the Decode phase of the Fetch Decode Execute Cycle. (1)

Answer 25

4. instruction held in CIR is decoded and split into opcode and operand

Question 26

What is opcode?

Answer 26

determines type of instruction and what hardware to execute it

Question 27

What is operand?

Answer 27

address where the operation is performed

Question 28

State the Execute phase of the Fetch Decode Execute Cycle. (1)

Answer 28

5. Appropriate instruction/opcode carried out in operand and executed