Information
Universal Serial Bus Interface
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
13-58 Freescale Semiconductor
specified in the queue head). Note that some of the field descriptions in Table 13-55 reference fields are
defined in the queue head. See Section 13.5.6, “Queue Head,” for more information on these fields.
Table 13-55. qTD Token (DWord 2)
Bits Name Description
31 dt Data toggle. This is the data toggle sequence bit. The use of this bit depends on the setting of the
Data Toggle Control bit in the queue head.
30–16 Total Bytes to
Transfer
Total bytes to transfer. This field specifies the total number of bytes to be moved with this transfer
descriptor. This field is decremented by the number of bytes actually moved during the transaction,
only on the successful completion of the transaction. The maximum value software may store in this
field is 5 4K (0x5000). This is the maximum number of bytes 5 page pointers can access. If the
value of this field is zero when the host controller fetches this transfer descriptor (and the active bit
is set), the host controller executes a zero-length transaction and retires the transfer descriptor. It is
not a requirement for OUT transfers that total bytes to transfer be an even multiple of QH[Maximum
Packet Length]. If software builds such a transfer descriptor for an OUT transfer, the last transaction
will always be less than QH[Maximum Packet Length]. Although it is possible to create a transfer up
to 20K this assumes the page is 0. When the offset cannot be predetermined, crossing past the 5th
page can be guaranteed by limiting the total bytes to 16K. Therefore, the maximum recommended
transfer is 16K (0x4000).
15 ioc Interrupt on complete. If this bit is set, the host controller should issue an interrupt at the next
interrupt threshold when this qTD is completed.
14–12 C_Page Current rage. This field is used as an index into the qTD buffer pointer list. Valid values are in the
range 0x0 to 0x4. The host controller is not required to write this field back when the qTD is retired.