NO:
W90P710 Programming Guide
VERSION:
2.1
PAGE:
79
The above information is the exclusive intellectual property of Winbond Electronics and shall not be disclosed,
distributed or reproduced without permission from Winbond.
Table No.: 1200-0003-07-A
one of the
HCCA
InterruptTable entries. The Isochronous
ED
list is linked to the last
ED
of the
Interrupt
ED
list.
While receiving an
IRP
from USB Driver,
HCD
must identify the target endpoint of this
IRP
and try
to find out the
ED
corresponding to the endpoint. If the
ED
does not exist,
HCD
must create a new
ED
and link it to the appropriate
ED
list. The
Endpoint Descriptor
s in an
ED
list are linked together by the
NextED
field of each
ED
. Each
NextED
links to the very next
ED
in an
ED
list. The
NextED
of the last
Endpoint Descriptor
must points to
zero
to signify the end of an
ED
list.
To add an
Endpoint Descriptor
to an
ED
list,
HCD
should write physical address of the new
ED
to
the
NextED
of the last
ED
and write
zero
to the
NextED
of the new
ED
.
To remove an
Endpoint Descriptor
,
HCD
should find the previous
ED
of the
ED
to be removed.
HCD
modified the
NextED
of the previous
ED
to point to the next
ED
of the
ED
to be removed, or
clear it if the
ED
to be removed is the last
ED
. However, before removing an
ED
,
HCD
must make
sure that
Host Controller
is not processing this
ED
and there’s no any
TD
waiting for service.
HCD
can temporarily disable the processing of target
ED
list by configuring
HcControl
register and enable
the SOF interrupt. In the next the SOF interrupt,
HCD
can guarantee that the
ED
list is not processed
by
Host Controller
.
Figure 6-4 Remove an Endpoint Descriptor
