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Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 441
UG585 (v1.11) September 27, 2016
Chapter 15: USB Host, Device, and OTG Controller
Note: The HCD should write only periodic schedule items (QH, iTD, siTD, FSTN) into the periodic
schedule. When using QH, it is an interrupt endpoint.
15.10.3 Asynchronous Schedule
The asynchronous schedule includes a circular list of queue heads for control and bulk transfers. The
host controller executes the data transfers after the periodic schedule is handled. This happens:
after the controller processes the periodic list
the periodic list is disabled, or
the periodic list is empty.
Table 15-20: USB Host Periodic Frame List Element Bit Fields
Bits Bit Field
Description
31:5 Pointer
Frame List Link Pointer (system memory pointer, 32-byte aligned):
The referenced object might be:
an isochronous transfer descriptor (iTD for HS devices),
a split-transaction isochronous transfer descriptor (siTD for FS
isochronous endpoints), or
a queue head (QH for FS/LS/HS interrupts).
4:3 reserved
Set = 00.
2:1 TYP
Transaction Descriptor Type, TYP. Refer to section 15.12.2 Transfer
Descriptor Type (TYP) Field.
0T
Terminate Linking, T:
0: Continue linking using Frame List Link Pointer.
1: Terminate transaction (done), host controller ignores the link pointer.