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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—USB 1.1 Device
Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
280
Order Number: 306262-004US
Data flow is relative to the USB host. IN packets represent data flow from the UDC to
the USB host. OUT packets represent data flow from the USB host to the UDC.
The FIFOs for the bulk and isochronous endpoints are double-buffered so that one
packet can be processed while the next is being assembled. While the UDC is busy
transmitting an IN packet from a particular endpoint, the Intel XScale processor can be
loading the same endpoint for the next frame transmission. Likewise, while the Intel
XScale processor is unloading an OUT endpoint, the UDC can continue to process the
next incoming packet to that endpoint.
8.3
USB Operation
After an Intel XScale processor reset — or when the USB host issues a USB reset — the
UDC configures all endpoints and is forced to use the USB default address, 0. After the
UDC configures the endpoints, the USB host assigns the UDC a unique address. At this
point, the UDC is under the USB host’s control and responds to commands that use
control transactions to transmit to endpoint 0.
The following sections provide details of the USB protocol in a bottom-up fashion,
starting with signalling levels.
8.3.1
Signalling Levels
USB uses differential signalling to encode data and to indicate various bus conditions.
The USB specification refers to the J and K data states to differentiate between high-
and low-speed transmission. Because the UDC supports only 12-Mbps transmission,
references are made only to actual data state 0 and actual data state 1.
Table 107.
Endpoint Configuration: Universal Serial Bus Device Controller
Endpoint Number
Type
Function
FIFO Size (bytes) X
Number of FIFOs
0
Control
IN/OUT
16
1
Bulk
IN
64x2
2
Bulk
OUT
64x2
3
Isochronous
IN
256x2
4
Isochronous
OUT
256x2
5
Interrupt
IN
8
6
Bulk
IN
64x2
7
Bulk
OUT
64x2
8
Isochronous
IN
256x2
9
Isochronous
OUT
256x2
10
Interrupt
IN
8
11
Bulk
IN
64x2
12
Bulk
OUT
64x2
13
Isochronous
IN
256x2
14
Isochronous
OUT
256x2
15
Interrupt
IN
8