Information

Universal Serial Bus Interface
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
13-66 Freescale Semiconductor
This area is characterized as an overlay because when the queue is advanced to the next queue element,
the source queue element is merged onto this area. This area serves an execution cache for the transfer.
Table 13-61 describes the host-controller rules for bits in overlay.
13.5.7 Periodic Frame Span Traversal Node (FSTN)
The periodic frame span traversal node (FSTN) data structure, shown in Figure 13-42, is to be used only
for managing full- and low-speed transactions that span a host-frame boundary. Software must not use an
FSTN in the asynchronous schedule. An FSTN in the asynchronous schedule results in undefined
behavior. Software must not use the FSTN feature with a host controller whose HCIVERSION register
indicates a revision implementation under 0x0096. Note that FSTNs were not defined for EHCI
implementations before Revision 0.96 of the EHCI Specification and their use may yield undefined results.
Table 13-61. Host-Controller Rules for Bits in Overlay (DWords 5, 6, 8, and 9)
DWord
QH
Offset
Bits Name Description
5 0x14 4–1 NakCnt Nak counter—RW. This field is a counter the host controller decrements
whenever a transaction for the endpoint associated with this queue head results
in a Nak or Nyet response. This counter is reloaded from RL before a transaction
is executed during the first pass of the reclamation list (relative to an
Asynchronous List Restart condition). It is also loaded from RL during an overlay.
6 0x18 31 dt Data toggle. The Data toggle control controls whether the host controller
preserves this bit when an overlay operation is performed.
6 0x18 15 ioc Interrupt on complete. The ioc control bit is always inherited from the source qTD
when the overlay operation is performed.
6 0x18 11–10 Cerr Error counter. Copied from the qTD during the overlay and written back during
queue advancement.
6 0x18 0 Status[0] Ping state (P)/ERR. If the EPS field indicates a high-speed endpoint, then this
field should be preserved during the overlay operation.
8 0x20 7–0 C-prog-mask Split-transaction complete-split progress. Initialized to zero during any overlay.
This field is used to track the progress of an interrupt split-transaction.
9 0x24 11–5 S-bytes Software must ensure that the S-bytes field in a qTD is zero before activating the
qTD. Keeps track of the number of bytes sent or received during an IN or OUT
split transaction.
9 0x24 4–0 FrameTag Split-transaction frame tag. Initialized to zero during any overlay. This field is used
to track the progress of an interrupt split-transaction.
313029282726252423222120191817161514131211109876543210offset
Normal Path Link Pointer 00 Typ T 0x00
Back Path Link Pointer 00 Typ T 0x04
Figure 13-42. Frame Span Traversal Node Structure