| 摘要 |
PURPOSE: An USB audio device circuit is provided to make an operation frequency of an USB audio device be synchronous with an operation frequency of an USB PC by realizing a feedback control logic. CONSTITUTION: A universal serial bus(USB) device circuit performs an USB isochronoustransmission with regard to wave data converted into an USB protocol at an USB PC(30) supporting the USB. A sampling clock generator(41) generates a sampling clock signal, a data start signal and sixteen times a signal of the sampling clock signal. A FIFO(42) stores the wave data, and transfers the stored wave data according to an input of the sampling clock signal, the data start signal and sixteen times the signal of the sampling clock signal. An audio digital-to-analog converter(DAC) (43) receives the wave data of the FIFO to output an analog sound signal. A feedback control logic part(44) counts the number of the wave data entering from the FIFO to the audio DAC to transfer the counted value to the USB PC. An USB device controller(45) processes the wave data of the USB PC into periodic data of a frame unit of 1ms to store the wave data thus processed to the FIFO.
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