1. Systems Architecture Keywords Fetch Execute Cycle
Von Neumann Architecture, MAR (Memory Address Register), MDR (Memory Data Register), Program Counter, Accumulator, ALU (Arithmetic Logic Unit), CU (Control Unit), Cache, Fetch/Execute, Busses.
Systems Architecture
Fetch Execute Cycle

2. Internal CPU Diagram Objectives Diagram Answer:
BEGINNER: Define CPU keywords and label an internal CPU diagram.
ADVANCED:
Describe and explain the MAR, MDR, Accumulator, ALU, CU, Cache and Program counter.
EXPERT:
Explain how the fetch-execute cycle works.
Task: Define the keywords and then label the internal CPU diagram.
Diagram Answer: PC
MAR
CIR
MDR
ALU
Accumulator
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
INP
Add 5
STO 8
ADD 8
Address Bus
Data Bus
Processor
Main Memory
Starter activity

3. Computer System Components
Objectives
BEGINNER: Describe the purpose and state the function of a CPU.
ADVANCED:
Explain common characteristics of a CPU and how they effect performance.
EXPERT:
State the purpose of embedded systems and give examples.
Internal Parts
The processor
Main memory (RAM, ROM, EEPROM)
I/O controllers
Buses
External Parts
Starter activity
Peripherals
I/O Devices / I/O Ports
Secondary Storage

4. Definitions Processor Objectives Main Memory - RAM
BEGINNER: Describe the purpose and state the function of a CPU.
ADVANCED:
Explain common characteristics of a CPU and how they effect performance.
EXPERT:
State the purpose of embedded systems and give examples.
Processor
The “brains” of the computer
Carries out instructions (Executes Instructions)
Processes Data
Retrieves Data/Instructions from Main Memory (Fetch)
Stores Data into Main Memory once Executed
Main Memory - RAM
Starter activity
Holds Data and Instructions that are currently in use by the processor
Located on the Motherboard
Directly Accessible by the processor
All data/instructions are lost once power is turned off

5. Definitions Main Memory - ROM Objectives Main Memory - EEPROM
BEGINNER: Describe the purpose and state the function of a CPU.
ADVANCED:
Explain common characteristics of a CPU and how they effect performance.
EXPERT:
State the purpose of embedded systems and give examples.
Main Memory - ROM
Instructions are permanently etched onto a ROM Chip
When power is turned off – instructions still remain on the ROM chip.
Bootstrap Loader is held in ROM
Gives the instructions to start up the Operating System
Main Memory - EEPROM
Starter activity
EEPROM – Electronically Erasable Programmable Read Only Memory
E.g. Sim cards / Flash Memory
Instructions/Data can be erased electronically and replaced

6. Definitions I/O Controllers Objectives System Busses
BEGINNER: Describe the purpose and state the function of a CPU.
ADVANCED:
Explain common characteristics of a CPU and how they effect performance.
EXPERT:
State the purpose of embedded systems and give examples.
I/O Controllers
These are used to allow an interface between a hardware device external to the motherboard (e.g. a Keyboard) and the Processor itself.
I/O controllers are used for:
Keyboard, Mouse, Disk Drive, VDU
System Busses
Starter activity
A bus is a set of parallel wires connecting two or more independent components of a computer system in order to pass signals between them.
The System is split into three separate busses:
The data bus
The address bus
The control bus

7. Definitions Address Bus Objectives Data Bus
BEGINNER: Describe the purpose and state the function of a CPU.
ADVANCED:
Explain common characteristics of a CPU and how they effect performance.
EXPERT:
State the purpose of embedded systems and give examples.
Address Bus
Carries addresses from the Processor to main memory or other I/O devices
It is one direction (Uni-Directional)
The processor generates an address
All data/Instructions are returned on the Data Bus
Data Bus
Starter activity
Carries Data/Instructions from Main Memory to the Processor (or from other secondary storage devices) to the processor.
Bi-Directional (two way)
Data can be read/written

8. Definitions Control Bus Objectives Peripherals
BEGINNER: Describe the purpose and state the function of a CPU.
ADVANCED:
Explain common characteristics of a CPU and how they effect performance.
EXPERT:
State the purpose of embedded systems and give examples.
Control Bus
Control signals are sent along the control bus
E.g. Memory Read, Memory Write
This instructs which was data will be travelling to/from memory.
Peripherals
Starter activity
Peripherals are any devices that are not directly connected to the CPU
E.g. mouse, keyboard, printer, hard disk drive, cd-rom drive
These devices are known as I/O devices (Input/Output Devices)

9. Definitions I/O Ports Objectives Secondary Storage
BEGINNER: Describe the purpose and state the function of a CPU.
ADVANCED:
Explain common characteristics of a CPU and how they effect performance.
EXPERT:
State the purpose of embedded systems and give examples.
I/O Ports
I/O Ports allow communication from an I/O device and the motherboard (hence CPU)
Secondary Storage
Starter activity
Used for long term storage of data and instructions
Hard Disk Drive
Solid State Drive
Flash Memory
DVD-R
Blu-ray

10. Fetch
Objectives
BEGINNER: Describe the purpose and state the function of a CPU.
ADVANCED:
Explain common characteristics of a CPU and how they effect performance.
EXPERT:
State the purpose of embedded systems and give examples.
Program counter is incremented for each instruction of the program being executed
The contents of the Program Counter are put into the MAR (Memory Address Register)
The address is transferred along the Address Bus to Main Memory (this address indicates which part of memory to fetch the data/instructions from
The data/instruction that has been addressed is transferred back to the processor along the data bus
This is held in the Memory Data Register
The instruction would then be transferred to the Current Instruction Register.
Starter activity

11. Registers Objectives Program Counter Memory Address Register
BEGINNER: Describe the purpose and state the function of a CPU.
ADVANCED:
Explain common characteristics of a CPU and how they effect performance.
EXPERT:
State the purpose of embedded systems and give examples.
Program Counter
Memory Address Register
Holds the location of the next instruction/data address in Main Memory
The contents of the PC are copied here and then transferred along the Address Bus
Memory Data Register
Current Instruction Register
Once Data/Instructions are brought from the Memory Address in Main Memory – they are placed in the MDR.
The instructions stored in the MDR are copied here
Starter activity

12. Decode/Execute
Objectives
BEGINNER: Describe the purpose and state the function of a CPU.
ADVANCED:
Explain common characteristics of a CPU and how they effect performance.
EXPERT:
State the purpose of embedded systems and give examples.
The instruction to be decoded is held in the Current Instruction Register
The instruction is split into an Op-Code and an Operand
The instruction is carried out by the ALU (Arithmetic Logic Unit)
ALU
Accumulator
Control Unit
Performs arithmetic and logical operations including +, -, AND, OR
Results of calculations are placed into the Accumulator
Sends Control Signals between the different internal components:
Memory Read
Memory Write
Hard Disk Drive Read
I/O Write
Starter activity