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Universal Serial Bus Interface – On-The-Go Module
10-50
Freescale Semiconductor
Figure 10-40. End Point Queue Head Organization
10.5.2.1
Endpoint Queue Head
All transfers are managed in the device endpoint queue head (dQH). The dQH is a 48-byte data structure,
but must align on 64-byte boundaries. During priming of an endpoint, the dTD (device transfer descriptor)
copies into the overlay area of the dQH, which starts at the nextTD pointer longword and continues
through the end of the buffer pointers longwords. After a transfer is complete, the dTD status longword
updates in the dTD pointed to by the currentTD pointer. While a packet is in progress, the overlay area of
the dQH acts as a staging area for the dTD so the device controller can access needed information with
minimal latency.
shows the endpoint queue head structure.
Endpoint QH1 - Out
Endpoint QH0 - In
Endpoint QH0 - Out
ENDPOINTLISTADDR
Endpoint Queue Heads
(up to 8 elements)
Transfer
Buffer
Transfer Buffer
Pointer
Transfer
Buffer
Transfer
Buffer
Transfer
Buffer
Transfer Buffer
Pointer
Endpoint
Transfer
Descriptors
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...