A USB transmission control circuit of the present invention includes: a USB data control unit, which outputs transmission data to a USB bus; a USB transmission scheduler circuit, which designates the USB data control unit to perform transmission; FIFO memory, which stores data from an external memory; a FIFO controller, which controls the FIFO memory; a bus arbiter, which performs bus usage arbitration; a DMA controller; calculation means for calculating the difference between the amount of data written into FIFO memory by the FIFO controller and the amount of data sent out to the USB bus; and transmission means for commencing data transmission to the USB bus in conformity with an acknowledge signal from the bus arbiter, which authorizes bus usage, in response to a DMA request for writing data into FIFO memory.
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