AN 702: Interfacing a USB PHY to the Hard Processor System USB 2.0 OTG Controller

ID 683601
Date 9/22/2017
Public
Document Table of Contents

1.1. ULPI Signals

Table 1.   Signals Included in the ULPI Interface

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.