What is Instruction cycle

Instruction cycle is the basic operating of computer who contain two cycle which are Fetch Cycle and Execute cycle.

Fetch Cycle

Fetch cycle is the cycle that fetch data or next instruction from the main memory into the CPU.During the Fetch Cycle ,there are 4 register are involved which are PC , MAR , MBR and IR. Generally the process in the

Fetch Cycle can be depicted by:
MAR ← PC (specify address in MM for the next read/write)
MBR ← M (MAR) (data to be written/received from memory)
PC ← PC + 1 (hold address to be fetched next. CPU increment the PC after each instruction)
IR ← (MBR) (fetched instruction is loaded into register)

Execute Cycle

Execute cycle is the cycle that interpret the opcode and perform the indicated operation.
The followings are steps that are involve in execute cycle:

1. Instruction decoding (to determine the operation that has to be performed by the CPU)
2. Operand (data) fetching
3. Data Processing
4. Store Result

The sequences of operations that happen in execution cycle differ according to the type of instruction.