I was asked for more detail about the fetch execute cycle. So I thought I would look for something new and a simpler way to explain it. So if you have a look at this BBC page, you should get a basic overview of what is happening. You can then read what I found on this page, this will help you to understand it a little better.
Then you can read my blog post about it, which also includes a link to an animation.
When I was learning the cycle I had to imagine it in my head as a warehouse with people, I used to work in a warehouse so it worked for me.
- At the start of the cycle the boss (processor) gives a runner (address bus) a piece of paper with the name (address) of the thing he wants.
- The runner hangs around till the boss shouts at him (read line activated).
- The runner the goes and finds the box his boss is looking (memory location) for in the warehouse (RAM) and uses a hand truck (Data bus) as it is heavy to place it on the bosses desk (processors register).
- The boss them opens the box (decode) and uses (execute) the photocopier inside.
The main steps are.
Fetch Execute Cycle
- Processor sets up address bus with correct address
- Processor activates read line on control bus
- Instruction from memory location is placed on to data bus and transferred to processor’s register
- Instruction is decoded and executed
