| Jerry | Date: Monday, 26/09/2011, 12:01 PM | Message # 1 |
 Ford Everest
Group: Administrators
Messages: 137
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| Machine Instruction Cycle
The machine instruction cycle includes the 4 steps: fetch, decode, execute, and store
This is how all function of the processor are carried out.
Diagram of the Machine Instruction Cycle
1.Fetch the instruction
*The in the program counter stored address is the address which contains next instruction that is to be executed.
*Via data bus the content of address contained in the program counter is fetched from the main memory & stored in the CIR (Current Instruction Register)
*Program counter = incremented by 1
2.Decode the instruction
*The instruction decoder interprets the instruction
*All required data = fetched from main memory & put in data registers
3.Execute the instruction
*CU passes decoded instruction to different parts of CPU to perform the actions that are required.
4.Store results
*Results of calculations in CPU = stored in main memory or sent to output devices
*Program Counter could be updated to a new address
REPEAT
1. Fetch cycle
Steps 1 and 2 of the Instruction Cycle are called the Fetch Cycle. These steps are the same for each instruction. The fetch cycle processes the instruction from the instruction word which contains an opcode and an operand.
Mashine Instructuon Cycle
2. Execute cycle
Steps 3 and 4 of the Instruction Cycle are part of the Execute Cycle. These steps will change with each instruction.
The first step of the execute cycle is the Process-Memory. Data is transferred between the CPU and the I/O module. Next is the Data-Processing uses mathematical operations as well as logical operations in reference to data. Central alterations is the next step, is a sequence of operations, for example a jump operation. The last step is a combined operation from all the other steps.
(http://wapedia.mobi/en/Instruction_cycle)
First video example of the Machine Instruction Cycle:
Second video example of the Machine Instruction Cycle:
Additional links:
http://www.it.jcu.edu.au/Subject....de.html (A more detailed explanation)
Machine Instruction Cycle (Interactive Flash animation from www.ib-computing.com)
Sources:
"Instruction Cycle." Wikipedia. 28 August 2010. Wikimedia.org. 2 September 2010. https://secure.wikimedia.org/wikipedia/en/wiki/Instruction_cycle
Jones, Richard. Computer Science Java Enabled. Victoria : IBID Press, 2004.
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