Qtd Next Element Transfer Pointer (Dword 0); Qtd Alternate Next Element Transfer Pointer (Dword 1); Next Qtd Pointer; Alternate Next Qtd Pointer - Intel IXP45X Developer's Manual

Intel
9.13.5.1

Next qTD Pointer

The first DWord of an element transfer descriptor is a pointer to another transfer
element descriptor.
Table 156.

qTD Next Element Transfer Pointer (DWord 0)

Bit
31:5
4:1
0
9.13.5.2

Alternate Next qTD Pointer

The second DWord of a queue element transfer descriptor is used to support hardware-
only advance of the data stream to the next client buffer on short packet. To be more
explicit the host controller will always use this pointer when the current qTD is retired
due to short packet.
Table 157.

qTD Alternate Next Element Transfer Pointer (DWord 1)

Bit
31:5
4:1
0
9.13.5.3

qTD Token

The third DWord of a queue element transfer descriptor contains most of the
information the host controller requires to execute a USB transaction (the remaining
endpoint-addressing information is specified in the queue head).
Note: The field descriptions forward reference fields defined in the queue head. Where
necessary, these forward references are preceded with a QH notation.
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Intel IXP45X and Intel IXP46X Product Line of Network Processors
Developer's Manual
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IXP45X and Intel IXP46X Product Line of Network Processors—USB 2.0 Host Controller
Next Transfer Element Pointer. This field contains the physical memory address of
the next qTD to be processed. The field corresponds to memory address signals[31:5],
respectively.
(Reserved). These bits are reserved and their value has no effect on operation.
Terminate (T).
0 = Pointer is valid (points to a valid Transfer Element Descriptor).
1 = pointer is invalid.
This bit indicates to the Host Controller that there are no more valid entries in the
queue.
Alternate Next Transfer Element Pointer. This field contains the physical memory address
of the next qTD to be processed in the event that the current qTD execution encounters a
short packet (for an IN transaction). The field corresponds to memory address signals [31:5],
respectively.
(Reserved). These bits are reserved and their value has no effect on operation.
Terminate (T).
0 = Pointer is valid (points to a valid Transfer Element Descriptor).
1 = pointer is invalid.
This bit indicates to the Host Controller that there are no more valid entries in the queue.
Description
Description
Order Number: 306262-004US
August 2006