| 摘要 |
An apparatus and method for monitoring USB keystroke data sent between a host ( 1 ) and keyboard ( 4 ) which allows the differentiation and monitoring between USB data sent at full speed (12 Mbps) and low speed (1.5 Mbps) on a USB data line ( 2 ). The differentiation is achieved by detecting when full speed USB data has been sent by detecting the single ended zero (SE0) condition of the previous packet and measuring the pulse width in the subsequent synchronisation sequence and detecting when low speed USB data has been sent by detecting the presence of a preamble packet or measuring the pulse width of the synchronisation sequence. Thus, the monitoring and differentiation between mixed said low speed and said full speed USB data is allowed which enables a USB keystroke recording apparatus ( 3 ) to ensure that keystroke data is not missed.
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