The instruction cycle is the entire sequence when a microcontroller executes instructions, and consists of the following operations.
Instruction fetch:Loading of instruction code
Instruction decoding:Analysis of instruction code
Instruction execution:Execution of instruction based on analysis results
Since each operation is carried out based on the clock cycle, the instruction cycle may be expressed as a total number of clocks that is needed for all the operations. However, most existing RISC microcontrollers previously load instruction code to a prefetch queue and process multiple instructions in parallel in a pipeline, and since instruction fetch and decoding cannot be seen externally, it is common to list just the number of clocks for the execution cycle.
There are also microcontrollers that execute the next instruction without waiting for data write even in the execution cycle.