Information

Universal Serial Bus Interface
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
13-52 Freescale Semiconductor
13.5.4 Split Transaction Isochronous Transfer Descriptor (siTD)
All full-speed isochronous transfers through the internal transaction translator are managed using the siTD
data structure. This data structure satisfies the operational requirements for managing the split transaction
protocol.
Figure 13-39 shows the split-transaction isochronous transfer descriptor (siTD).
13.5.4.1 Next Link Pointer
DWord0 of a siTD is a pointer to the next schedule data structure. Table 13-46 describes the next link
pointer fields.
13.5.4.2 siTD Endpoint Capabilities/Characteristics
DWords 1 and 2 specify static information about the full-speed endpoint, the addressing of the parent
Companion Controller, and microframe scheduling control.
313029282726252423222120191817161514131211109876543210offset
Next Link Pointer 00 Typ T 0x00
I/O Port Number 0 Hub Address 0000 EndPt 0 Device Address 0x04
0000_0000_0000_00000 µFrame C-mask µFrame S-mask 0x08
ioc P
1
1
Host controller read/write; all others read-only.
0000 Total Bytes to Transfer
1
µFrame C-prog-mask
1
Status
1
0x0C
Buffer Pointer (Page 0) Current Offset
1
0x10
Buffer Pointer (Page 1) 000_0000 TP
1
T-count
1
0x14
Back Pointer 0000 T 0x18
Figure 13-39. Split-Transaction Isochronous Transaction Descriptor (siTD)
Table 13-46. Next Link Pointer
Bits Name Description
31–5 Next Link
Pointer
This field contains the address of the next data object to be processed in the periodic list and
corresponds to memory address signals [31:5], respectively.
4–3 — Reserved, should be cleared. These bits must be written as zeros.
2–1 Typ Indicates to the host controller whether the item referenced is an iTD/siTD or a QH. This allows the host
controller to perform the proper type of processing on the item after it is fetched. Value encodings are:
00 iTD (isochronous transfer descriptor)
01 QH (queue head)
10 siTD (split transaction isochronous transfer descriptor
11 FSTN (frame span traversal node)
0 T Terminate.
0 Link pointer is valid.
1 Link pointer field is not valid.