Fetch-Execute Cycle

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1.

The address of the next instruction to be executed is copied from the  RAM into the MAR.

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2.

The instruction held at the copied address, which is now in the MAR, is copied to the MBR.

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3.

At the same time as the last step, the value stored in the PC is incremented by 1.

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4.

The instruction(s) held in the MBR are copied to the CIR ready to be executed.

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Execution phase (1)

The instruction stored in the CIR is decoded into a format that can be inputted into the CPU's logic circuits.

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Execution phase (2)

The instruction held in the CIR is then executed through the CPU's logic circuits.

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Glossary

Program counter (PC) - This indicates the location in the CPU cache of the next instruction in the sequence. This is incremented after each fetch.

Memory address register (MAR) - this stores the addresses of instructions waiting to be fetched and executed.

Memory buffer register (MBR) - This is a buffer containing instructions waiting to be decoded and executed.

Current instruction register (CIR) - This is where the current instruction being executed is stored.

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Comments

Grasshopper

I think the text could be a lot bigger and/or bolder so it is easier to see and so, I think,  will be easier to remember

alexandermclarke

Thank for the feedback. I've edited it now :)

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