A system on chip (SoC) includes a control circuit configured to determine whether a requested operating mode is one of a functional mode and a monitoring mode. The control circuit is configured to provide a request signal to at least one clock circuit to request at least one clock signal and selectively output one of the at least one clock signal in response to at least one acknowledgment signal received from the at least one clock circuit, when the requested operating mode is the functional mode. The control circuit is configured to selectively output one of the at least one clock signal without providing the request signal, when the requested operating mode is the monitoring mode.