AN 702: Interfacing a USB PHY to the Hard Processor System USB 2.0 OTG Controller
1.1. ULPI Signals
| Signal |
Description |
|---|---|
| CLK |
Interface clock—All signals are synchronous to the clock. |
| DATA[7:0] |
Data bus—Driven low by the controller during idle. The controller starts a transfer by sending a non-zero pattern. The PHY must assert DIR before using the data bus. Every time DIR toggles, DATA must be ignored for one clock cycle (the turnaround cycle). |
| DIR |
Direction of the data bus—By default, DIR is low and the PHY listens for non-zero data from the controller. The PHY asserts DIR to get control of the data bus. |
| NXT |
Next data—The PHY drives NXT high to throttle the data bus. |
| STP |
Stop data—The controller drives STP high to signal the end of the data stream. The controller can also drive STP high to request data bus access from the PHY. |