11.3.2.2 describe the purpose of CPU components, system bus and main memory

System bus

System bus (extended in grade 12)

Bus - microscopic parallel wires that transmit data between internal components.

The main bus is the SYSTEM BUS

Its actually made up of 3 separate buses, but when we join them together we can just call it the System Bus

System bus – the main highway connecting the CPU, the main memory and I/O controllers. It is made up of a data bus, an address bus and a control bus.

Address Bus

Function: Carries the address of the location to be accessed (for either read or write).

Unidirectional: The CPU sends out addresses on this bus to the main memory or other I/O devices to select a location for reading or writing, but devices don't send addresses back to the CPU on this bus.

Width: The width (number of wires or lines) determines how many memory locations can be addressed. For example, a 16-bit wide address bus can access 2^16 or 65,536 unique memory locations.

Data Bus

Function: Transfers actual data between the CPU and memory or I/O devices.

Bidirectional: Data can flow both ways. The CPU can read data from memory or write data to it.

Width: The width of the data bus (often called the word size) often determines the amount of data a CPU can process at once. For example, a 32-bit data bus can transfer 32 bits of data in a single operation.

Control Bus

Function: Carries control signals to manage and direct the operation of the entire computer system. These signals can indicate whether a current operation is a read or write, whether the system should interrupt the current process, etc.

Bidirectional: Some control lines are unidirectional, while others might be bidirectional, depending on the nature of the control signal.

Signals: Some common control signals include:

• Read (indicating a read operation)
• Write (indicating a write operation)
• Interrupt Request (IRQ, from devices wanting the CPU's attention)
• Memory Write (signal to write to a memory location)
• Bus Request (when a component wants control of the bus)
• Reset (to restart the CPU or other components)

Questions:

Exercises:

Ex.1 Define elements of the scheme