Udc Hardware Connections; Self-Powered Device; Bus-Powered Devices; Register Descriptions - Intel IXP45X Developer's Manual

USB 1.1 Device Controller—Intel
Processors
When the device responds to the host, it must specify a legal USB configuration. For
example, if the device specifies a configuration of six isochronous endpoints of
256 bytes each, the host is not able to schedule the proper bandwidth and does not
take the UDC out of Configuration 0. The user device determines which endpoints to
report to the host. If an endpoint is not reported, it is not used.
Another option, attractive — for use with isochronous endpoints — is to describe a
configuration of a packet with a maximum size less than 256 bytes to the host. For
example, if software responds to the GET_DESCRIPTOR command that Endpoint 3 only
supports 64 bytes maximum packet isochronous IN data, the user device must set the
UDCCS3[TSP] bit after it loads 64 bytes for transmission. Similarly, if Endpoint 4 is
described as supporting 128 bytes maximum packet Isochronous OUT data, the UDC
recognizes the end of the packet, sets UDCCS4[RPC], and an interrupt is generated.
The direction of the endpoints is fixed. Physically, the UDC only supports interrupt
endpoints with a maximum packet size of 8 bytes or less, bulk endpoints with a
maximum packet size of 64 bytes or less, and isochronous endpoints with a maximum
packet size of 256 bytes or less.
To make the IXP45X/IXP46X network processors more adaptable, the UDC supports a
total of four configurations. Each of these configurations are identical in the UDC,
software can make three distinct configurations, each with two interfaces.
Configuration 0 is a default configuration of Endpoint 0 and cannot be used in any other
configuration.
After the host completes a SET_CONFIGURATION or SET_INTERFACE command, the
software must decode the command to empty the OUT endpoint FIFOs and allow the
Intel XScale processor to set up the proper power/peripheral configurations.
8.4

UDC Hardware Connections

This section explains how to connect the USB interface for a variety of devices.
8.4.1

Self-Powered Device

The IXP45X/IXP46X network processors do not implement any low-power modes of
operation. Therefore, the UDC can be connected to act as a full-speed device in a
permanent configuration by pulling the USB_DPOS signal to a logic high.
The USB_DPOS signals should be pulled high by the 5-V signal received over the USB
connector. The ground received from the USB connector should be tied to the ground of
the board.
8.4.2

Bus-Powered Devices

The IXP45X/IXP46X network processors do not support bus-powered devices because
they cannot limit the amount of current consumed to 500 µA when the USB host issues
a suspend. (Section 7.2.3 of the USB Specification, version 1.1 requires that less than
500 µA is consumed when the USB host issues a suspend.)
8.5

Register Descriptions

All configuration, request/service, and status reporting is controlled by the USB host
controller and is communicated to the UDC via the USB. The UDC has registers that
control the interface between the UDC and the software.
August 2006
Order Number: 306262--, Revision: 004US
® ®
IXP45X and Intel IXP46X Product Line of Network
Intel
® ®
IXP45X and Intel IXP46X Product Line of Network Processors
Developer's Manual
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