US Patent 7089337 Controlling device connected to IEEE1394 serial bus

In the case where a rewind or fast-forward button is clicked after a playback button is clicked, a CPU on controller side sets a reproduction flag bit to “on” upon receipt of a response frame from a DV camcorder indicating that the playback command is normally accepted, without checking whether the DV camcorder is during playback operation or not, and determines what kind of control command should be sent to the DV camcorder based on the reproduction flag bit and the clicked button. The controller can determine the control command without waiting for the response to an inquiry about whether the DV camcorder is during playback operation or not, thus quickly sending a rewind playback or fast-forward playback command to the DV camcorder.