Data Buses

Data is transferred between the RAM and CPU via the system 'Buses'.

Data and control signals travel in both directions between the processor, memory and I/O controller along the buses. Addresses on the other hand, only travel one way along the address bus. The processor sends all  instructions/addresses to the RAM to be stored/retrieved to either the memory or I/O controller.

There are three types of 'bus':
  • Address Bus
    • Memory is divided into units called 'words' of a fixed size. Each 'word' has its own address. 
    • The address bus transmits the address of these 'words' that are required to be used in the program so the data can be found and sent back to the processor. 
    • All data is transmitted via the Data Bus. 
  • Data Bus
    • Consists of separate lines. Different processors have different amounts of lines. Either 6, 16, 32.....etc. 
    • Data/instructions can travel in both directions on the data bus. 
  • Control Bus
    • This transfers information about what is happening between the components (including status information about the components and timing info). 
    • It helps to make sure requests don't conflict each other and cause a freeze of the system (keeps everything running smoothly). 






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