Freescale Semiconductor TWR-MCF52259-Ethenet - Manual (Page 113)

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USB Signaling
• USB uses Non-Return to Zero, Inverted signaling
– Separate clock signal not required to be delivered with data
– ‘1’ on the data line indicates no change in level of NRZI signal
– ‘0’ on the data line indicates transition in level of NRZI signal
– Long string of 1s will eventually cause receiver to lose
synchronization
Idle 0 1 1 0 1 0 0 0 1 1 1 0
Data
NRZI