In one implementation, an electronic system includes a host and a data storage device. The data storage device includes a flash memory, a controller and a delay circuit. The controller is configured to receive a read command from the host, read a first data sector from the flash memory according to the read command, and produce a setting signal according to a maintenance time of the flash memory when the flash memory needs to be maintained. The delay circuit is configured to receive the setting signal from the controller, divide the first data sector into a plurality of first sub-data sectors according to the setting signal, and transmit at least one of the first sub-data sectors to the host at a predetermined time interval for extending a busy time of the controller.