A memory apparatus includes a host device and a slave device. The host device stores verification data. The slave device includes a memory unit, a control unit, and a logic unit. The control unit drives the memory unit to provide storage data in a data transmission sub-period, and further provides a control signal, indicating the first verification data, in a dummy sub-period. The logic unit provides first preamble data, indicating substantially a same data value as the verification data, in the dummy sub-period in response to the first control signal. The preamble data and the storage data are transmitted according to an internal clock signal. The host device samples the first preamble data according to an external clock signal, and determines whether the external and the internal clock signals are synchronized by comparing the first preamble data and the first verification data.