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Machine cylce/fetch exectute cycle (1 Viewer)
- Thread starter singhsta
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have a look at:
http://courses.cs.vt.edu/~csonline/MachineArchitecture/Lessons/CPU/Lesson.html
also check out and go through the flash animation links they help heaps....
but heres the paragraph which probably answres your question:
... Thus both inputs to the CPU are stored in memory, and the CPU functions by following a cycle of fetching an instruction, decoding it, and executing it. This process is known as the fetch-decode-execute cycle. The cycle begins when an instruction is transferred from memory to the IR along the data bus. In the IR, the unique bit patterns that make up the machine-language are extracted and sent to the Decoder. This component is responsible for the second step of the cycle, that is, recognizing which operation the bit pattern represents and activating the correct circuitry to perform the operation. Sometimes this involves reading data from memory, storing data in memory, or activating the ALU to perform a mathematical operation. Once the operation is performed, the cycle begins again with the next instruction. The CPU always knows where to find the next instruction because the Program Counter holds the address of the current instruction. Each time an instruction is completed, the program counter is advanced by one memory location.
hmm pretty much an instruction is fetched (the fetch part) from primary storage (RAM) and then sent to the instruction register. after which it is sent the decoder. At the decoder the instruction is decoded and the appropriate process is then carried out (execute stage). The process bascially repeats itself as necessary.... it's sometimes heard also as the fetch-decode-execute cycle....... but yeah the anims on that page a very good and simple to follow.
http://courses.cs.vt.edu/~csonline/MachineArchitecture/Lessons/CPU/Lesson.html
also check out and go through the flash animation links they help heaps....
but heres the paragraph which probably answres your question:
... Thus both inputs to the CPU are stored in memory, and the CPU functions by following a cycle of fetching an instruction, decoding it, and executing it. This process is known as the fetch-decode-execute cycle. The cycle begins when an instruction is transferred from memory to the IR along the data bus. In the IR, the unique bit patterns that make up the machine-language are extracted and sent to the Decoder. This component is responsible for the second step of the cycle, that is, recognizing which operation the bit pattern represents and activating the correct circuitry to perform the operation. Sometimes this involves reading data from memory, storing data in memory, or activating the ALU to perform a mathematical operation. Once the operation is performed, the cycle begins again with the next instruction. The CPU always knows where to find the next instruction because the Program Counter holds the address of the current instruction. Each time an instruction is completed, the program counter is advanced by one memory location.
hmm pretty much an instruction is fetched (the fetch part) from primary storage (RAM) and then sent to the instruction register. after which it is sent the decoder. At the decoder the instruction is decoded and the appropriate process is then carried out (execute stage). The process bascially repeats itself as necessary.... it's sometimes heard also as the fetch-decode-execute cycle....... but yeah the anims on that page a very good and simple to follow.
Last edited:
Saintly Devil
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Thanks!!!!!
That helps a lot. We have our major project as a CPU simulation program, and part of that is to figure out how the whole fetch/execute cycle works.
This is perfect.
That helps a lot. We have our major project as a CPU simulation program, and part of that is to figure out how the whole fetch/execute cycle works.
This is perfect.
