What are the different phases of an instruction cycle?

An instruction cycle has these phases:

• Fetch: the instruction is read from the memory address held in PC, and PC is incremented.
• Decode: the control unit finds out the operation from the opcode.
• Operand fetch: the effective address is found, and the operand is read from memory or a register.
• Execute: the ALU or another unit does the operation.
• Write back (store): the result is saved in a register or memory.

After this, the CPU may check for an interrupt, and then repeat the cycle for the next instruction.