Introduction
Instruction Cycle is the program residing in the memory until of the sequence of the instruction.
The program that executes in the system is going through cycle of each instruction.
Each instruction cycle is turn in sub-division into a sequence of sub-cycles or phases.
Instruction cycle is use to circulate the instruction through memory to processor for processing.
The phases of the instruction cycle are as follows:
1) Fetch the instruction from memory
2) Decode the instruction
3) Execute the instruction
The one more phase is also considered in them and that is read the instruction and allocate the memory for the instruction.
Means Read the effective address for the instruction from memory.
Elaboration of each phase of the instruction cycle
Fetch the instruction from memory: In this phase the instruction that given through user, and that is store in the memory, is need to fetch from memory for the decoding through which, the system is able to execute the instruction and give the appropriate response.
Decode the instruction: In this phase the instruction is going to decode, because when the instruction is stored in the memory, then the instruction is encoded for the security like and then the system try to decode it for the execution of the instruction.
Execution of the instruction: In this phase the instruction is going to execute, when the instruction is fetched and encoded then the system know what is the task and what needed in this task to complete then the system is in final stage where only one thing is left and that is execution.
Before execution one phase is also come and that is analyzing the effective address for the instruction by which after the execution the result is stored on that address or the temporary results or instruction store on that address during execution.
Diagram of Instruction Cycle
Working of the diagram
The instruction cycle is work on this cycle that is show in the given picture, First the system is start, after that the address is loaded to PC for the execution of the instructions that are given by the user, after that the content of the PC loaded to memory address register(MAR), after that the PC updates to new address, after that the data loaded to memory data register that required, after that the contents of memory address register transfer to current instruction register(CIR), then by the help of decoder the contents of CIR id decoded, after that if the jump is in yes mode then the PC is set to value from jump instruction, and if the jump is in no then the instruction is executed, now during the execution if there is no interrupt then the system execute the instruction and go up according to cycle and if the interrupt is occur then it can do services interrupt and try again. This process is done in every instruction process for the execution and it is very important for the effective response.
That is the full phase explanation and the full explanation of cycle.
The instruction cycle is very important part in the execution of the instruction in the system.
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