Rainbow Electronics W90P710CDG - Manual (Page 171)

W90P710CD/W90P710CDG
Publication Release Date: September 19, 2006
- 171 - Revision B2
6.7 USB Host Controller
The Universal Serial Bus (USB) is a low-cost, low-to-mid-speed peripheral interface standard
intended for modem, scanners, PDAs, keyboards, mice, and other devices that do not require a high-
bandwidth parallel interface. The USB is a 4-wire serial cable bus that supports serial data exchange
between a Host Controller and a network of peripheral devices. The attached peripherals share USB
bandwidth through a host-scheduled, token-based protocol. Peripherals may be attached, configured,
used, and detached, while the host and other peripherals continue operation (i.e. hot plug and unplug
is supported).
A major design goal of the USB standard was to allow flexible, plug-and-play networks of USB
devices. In any USB network, there will be only one host, but there can be many devices and hubs.
The USB Host Controller has the following features:
• Open Host Controller Interface (OHCI) Revision 1.0 compatible.
• USB Revision 1.1 compatible
• Supports both low-speed (1.5 Mbps) and full-speed (12Mbps) USB devices.
• Handles all the USB protocol.
• Built-in DMA for real-time data transfer
• Multiple low power modes for efficient power management
6.7.1 USB Host Functional Description
6.7.1.1 AHB Interface
The OpenHCI Host Controller is connected to the system by the AHB bus. The design requires both
master and slave bus operations. As a master, the Host Controller is responsible for running cycles
on the AHB bus to access EDs and TDs as well as transferring data between memory and the local
data buffer. As a slave, the Host Controller monitors the cycles on the AHB bus and determines when
to respond to these cycles. Configuration and non-real-time control access to the Host Controller
operational registers are through the AHB bus slave interface.
6.7.1.2 Host Controller
List Processing
The List Processor manages the data structures from the Host Controller Driver and coordinates all
activity within the Host Controller.
Frame Management
Frame Management is responsible for managing the frame specific tasks required by the USB
specification and the OpenHCI specification. These tasks are:
1) Management of the OpenHCI frame specific Operational Registers
2) Operation of the Largest Data Packet Counter.
3) Performing frame qualifications on USB Transaction requests to the SIE.
4) Generate SOF token requests to the SIE.