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Chapter 20
Universal Serial Bus Interface – Host Module
This chapter describes the universal serial bus (USB) host module, which implements many industry
standards. However, it is beyond the scope of this document to document the intricacies of these standards.
Instead, it is left to the reader to refer to the governing specifications. Readers of this chapter are assumed
to be fluent in the operation and requirements of a USB network.
The following documents are available from the USB Implementers Forum web page at
http://www.usb.org/developers/docs:
•
Universal Serial Bus Specification, Revision 2.0
The following documents are available from the Intel USB Specifications web page at
http://www.intel.com/technology/usb/spec.htm:
•
Enhanced Host Controller Interface (EHCI) Specification for Universal Serial Bus, Revision 1.0
20.1
Introduction
The processor implements two USB modules: a host module and an On-The-Go (OTG) module. The host
module is used with a full-speed/low-speed on-chip transceiver or . Whereas, the OTG module can be used
with the on-chip transceiver or with an external ULPI transceiver. For more details on the USB OTG
module, refer to
Chapter 21, "Universal Serial Bus Interface – On-The-Go Module."
USB host modules must supply 500 mA with a 5 V supply on its downstream port (referred to as VBUS).
If the connected device attempts to draw more than the allocated amount of current, the USB host must
disable the port and remove power. This processor provides pins for control and status to an external IC
capable of managing the VBUS downstream supply.
Register and data structure interfaces conform to the EHCI specification from Intel Corporation, with
enhancements to support the embedded environment. The USB controller contains its own DMA (direct
memory access) engines that reduce interrupt load on the application processor, and thereby reduce total
system bus bandwidth dedicated to servicing the USB interface requirements. The USB controller includes
logic to support USB's low-power suspend features, and for suspended devices to request remote wakeup
from the host.
This USB host controller hides all direct interaction with the protocol, but some knowledge of the USB is
required to properly configure the device for operation on the local bus and on the USB. This document
covers programming requirements, and additional information may be found in the USB specification.
Freescale Semiconductor
MCF5329 Reference Manual, Rev 3
20-1
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