A data storage device includes a power line communication (PLC) circuit and a storage controller. The PLC circuit is coupled to a power line. The storage controller is coupled to the PLC circuit. The storage controller is configured to access a plurality of memory block. The PLC circuit is configured to carry at least one signal outputted from the storage controller on the power line, in order to transmit the at least one signal to an external device such that an operational state of the data storage device can be debugged/monitored.