A method includes operation below. A first task is performed by a control circuit according to a first request from a processor. A second request, for triggering a second task to be performed by the control circuit, is received by an interface circuit. A first data rate, for transmitting first data generated in the first task, is calculated by the interface circuit. A second data rate, for transmitting second data to be generated in the second task, is estimated by the interface circuit. The second task other than the first task is performed by the control circuit. The first data and the second data are transmitted from the control circuit to the processor in a condition that a sum of the first data rate and the second data rate complies with a bandwidth of a data switch coupled between the control circuit and the processor.