Texas Instruments TMS320C6747 DSP 2.2 USB1 Module Open Host Controller Interface Functionality

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2.2USB1 Module Open Host Controller Interface Functionality

2.2.1OHCI Controller Overview

The Open HCI—Open Host Controller Interface Specification for USB, Release 1.0a defines a set of registers and data structures stored in system memory that control how a USB host controller interfaces to system software. This specification, in conjunction with the Universal Serial Bus Specification Version 2.0, defines most of the USB functionality that the USB host controller provides.

The OHCI Specification for USB focuses on two main aspects of the USB host controller hardware implementation: its register set and the memory data structures that define the appearance of USB bus activity. Other topics include interrupt generation, USB host controller state, USB frame management, and the hardware methods used to process the lists of data structures in system memory.

This document does not duplicate the information presented in the OHCI Specification for USB or the USB Specification. USB host controller users can refer to the USB Specification and the OHCI Specification for USB for detailed discussions of USB requirements and OHCI controller operation.

2.3USB1 Module Differences From OHCI Specification for USB

The USB1 Module OHCI compatible host controller implementation does not implement every aspect of the functionality defined in the OHCI Specification for USB. The differences focus on power switching, overcurrent reporting, and the OHCI ownership change interrupt. Other restrictions are imposed by the effects of the pin multiplexing options.

2.3.1Power Switching Output Pins Not Supported

The device does not provide pins that can be controlled directly by the USB host controller OHCI port power control features. The OHCI RHPORTSTATUS register port power control bits can be programmed by the USB host controller driver software, but this does not have any direct effect on any VBUS switching implemented on the board.

You can use software control of GPIO pins or other implementation-specific control mechanisms to control VBUS switching.

2.3.2Overcurrent Protection Input Pins Not Supported

The device does not provide any pins that allow the USB host controller OHCI RHPORTSTATUS overcurrent protection status bits to be directly controlled by external hardware.

You can use software monitoring of GPIO pins or other implementation-specific control mechanisms to report port overcurrent information to the USB host controller driver.

2.3.3No Ownership Change Interrupt

The USB host controller does not implement the OHCI ownership change interrupt.

SPRUFM8–September 2008 Universal Serial Bus OHCI Host Controller 9

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