| 摘要 |
PROBLEM TO BE SOLVED: To efficiently use a USB bus by efficiently reducing idle states on the USB bus in a small FIFO size, and reducing header parts other than substantial data in the USB packet and the number of times of transmission of a check code. SOLUTION: In this system provide with an FIFO memory, a bus arbiter, and a DMA controller 105 as means for transferring data between data in an external memory 102 and blocks 107 and 109 for generating USB transmission data, and a means for calculating the difference between the data quantity written in an FIFO memory 108 and the data quantity transmitted to a USB bus which is under the control of an FIFO controller 106, there is a transmitting means for starting the data transmission to a USB bus 122 according to an acknowledge signal 206 for permitting bus use from the bus arbiter 103, in response to a DMA request for data write in the FIFO memory 108.
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