12-2
Intel® PXA255 Processor
Developer’s Manual
USB Device Controller
12-Mbps device and provides the correct polarity for data transmission. The serial bus uses
differential signalling to transmit multiple states simultaneously. These states are combined to
produce transmit data and various bus conditions, including: Idle, Resume, Start of Packet, End of
Packet, Disconnect, Connect, and Reset.
12.2
Device Configuration
Table 12-1
shows the device’s configuration.
Data flow is relative to the USB host. IN packets represent data flow from the UDC to the host.
OUT packets represent data flow from the host to the UDC.
The FIFOs for the Bulk and Isochronous endpoints are double-buffered so one packet can be
processed as the next is assembled. While the UDC transmits an IN packet from a particular
endpoint, the Megacell can load the same endpoint for the next frame transmission. While the
Megacell unloads an OUT endpoint, the UDC can continue to process the next incoming packet to
that endpoint.
12.3
USB Protocol
After a core reset or when the USB host issues a USB reset, the UDC configures all endpoints and
is forced to use the USB default address, zero. After the UDC configures the endpoints, the host
assigns the UDC a unique address. At this point, the UDC is under the host’s control and responds
to commands that use control transactions to transmit to endpoint 0.
Table 12-1. Endpoint Configuration
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
Содержание PXA255
Страница 1: ...Intel PXA255 Processor Developer s Manual January 2004 Order Number 278693 002 ...
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Страница 30: ...1 6 Intel PXA255 Processor Developer s Manual Introduction ...
Страница 310: ...7 46 Intel PXA255 Processor Developer s Manual LCD Controller ...
Страница 330: ...8 20 Intel PXA255 Processor Developer s Manual Synchronous Serial Port Controller ...
Страница 358: ...9 28 Intel PXA255 Processor Developer s Manual I2 C Bus Interface Unit ...
Страница 488: ...13 36 Intel PXA255 Processor Developer s Manual AC 97 Controller Unit ...
Страница 572: ...16 30 Intel PXA255 Processor Developer s Manual Network SSP Serial Port ...
Страница 599: ...Intel PXA255 Processor Developer s Manual 17 27 Hardware UART ...
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