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Universal Serial Bus Interface
MCF5253 Reference Manual, Rev. 1
24-122
Freescale Semiconductor
NOTE
The software must ensure that no interface data structure reachable by the
Device Controller spans a 4K-page boundary.
The data structures defined in the section are (from the device controller's perspective) a mix of read-only
and read/ writable fields. The device controller must preserve the read-only fields on all data structure
writes.
The USB_DR core includes DCD software called the USB 2.0 Device API. The Device API provides an
easy to use Application Program Interface for developing device (peripheral) applications. The Device
API incorporates and abstracts for the application developer all of the elements of the program interface.
Figure 24-60. End Point Queue Head Organization
Device queue heads are arranged in an array in a continuous area of memory pointed to by the
ENDPOINTLISTADDR pointer. The even –numbered device queue heads in the list support receive
endpoints (OUT/SETUP) and the odd-numbered queue heads in the list are used for transmit endpoints
(IN/INTERRUPT). The device controller will index into this array based upon the endpoint number
received from the USB bus. All information necessary to respond to transactions for all primed transfers
is contained in this list so the Device Controller can readily respond to incoming requests without having
to traverse a linked list.
NOTE
The Endpoint Queue Head List must be aligned to a 2k boundary.
24.10.1 Endpoint Queue Head
The device Endpoint Queue Head (dQH) is where all transfers are managed. The dQH is a 48-byte data
structure, but must be aligned on 64-byte boundaries. During priming of an endpoint, the dTD (device
Up to
32 elements
Endpoint QH 0
– In
ENDPOINTLISTADDR
Endpoint QH 1
– Out
Endpoint
Transfer
Descriptor
Endpoint Queue Heads
Transfer Buffer Pointer
Transfer
Buffer
Transfer
Buffer
Transfer
Buffer
Transfer
Buffer
Transfer Buffer Pointer
Transfer Buffer
Pointer
Transfer
Buffer
Pointer
Endpoint QH 0
– Out
Содержание MCF5253
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Страница 46: ...MCF5253 Introduction MCF5253 Reference Manual Rev 1 1 14 Freescale Semiconductor...
Страница 62: ...Signal Description MCF5253 Reference Manual Rev 1 2 16 Freescale Semiconductor...
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