1.3.2(a): show understanding of the basic Von Neuman model for a computer system and the stored program concept

Address bus- Transmits signals relating to the addresses between the processor and memory – Unidirectional (One direction)

Data Bus – Transmits data between the processor, memory unit and I/O devices- Bidirectional (Both directions)

Control Bus- Transmits signals relating to control of all activities in the computer (e.g read and write)- unidirectional and bidirectional

Memory Unit:

The memory unit makes use of the Memory Address Registers (MAR) and the Memory Data Register(MDR)

The memory unit is made up of partitions. Each partition is made up of an address and the addresses contents

Read Operation

1. For example, read: 0000 0011
2. The address is written to the MAR
3. A read signal is sen to the memory unit via the control bus
4. The contents of this memory location are written to the MDR

MAR: 00000011
MDR: 11001011
Write Operation

1. For example, write: 1001 0010 to: 1111 1101
2. The contents are written to the MDR
3. The address of the location is written to the MAR.
4. A write signal is sent to the memory unit via the control bus

MAR: 11111101
MDR: 10010010

The MAR is where abouts the content is
The MDR is the content


Processor

Contains ALU(Arithmetic and Logic Unit)

Does math operations like addition and divide.

The ALU uses a register called the accumulator, which stores the results of its calculations

Control Unit
The control unit makes use of the Current Instruction Register (CIR) and the Program Counter (PC)

The control unit controls the operation of the CPU. It reads an instruction from memory (the address of the instruction is stored in the PC)

This instruction is interpreted and signals are transferred via the control to tell other components what to do.