A data processing apparatus which transmits a clock signal to a recording medium, transmits a command to the recording medium and receives data output from the recording medium in response to a timing signal obtained by delaying the clock signal. The apparatus transmits to the recording medium a transmission command in a predetermined data string including a predetermined pattern and receive the predetermined data output from the recording medium. The apparatus adjusts a delay amount of the timing signal based on a reception result of the predetermined data string in a first mode or second mode. The reception result is based on timing signals each including a delay amount, in a first range in the first mode and in a second range narrower than the first range in the second mode.