| 摘要 |
PURPOSE: A USB(Universal Serial Bus) test unit is provided, which reduces a time required in testing a USB transceiver after it is designed and fabricated. CONSTITUTION: According to the USB test unit, a data input/output part(100) outputs or inputs data to/from a data bus, and comprises a differential amplifier(120), and generates a logic value of a high level in case of a normal state by differentially amplifying positive data(D+) and negative data(D-). A cross over voltage detection unit(200) detects a time when a cross over occurs and latches a voltage at this time. And a timing detection part(300) detects and judges a rising time and a falling time of data by counting an external clock(FCLK) having a constant frequency by generating an enable signal when a potential level of the positive data and the negative data lies within a range according to a USB standard.
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