Cirrus Logic EP93xx - Manual (Page 453)

DS785UM1 11-13
Copyright 2007 Cirrus Logic
Universal Serial Bus Host Controller
EP93xx User’s Guide
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Definition:
Controls the host controller’s operating modes.
Bit Descriptions:
RSVD: Reserved. Unknown During Read.
CBSR: ControlBulkServiceRatio:
This specifies the service ratio between Control and Bulk
EDs. Before processing any of the nonperiodic lists, HC
must compare the ratio specified with its internal count on
how many nonempty Control EDs have been processed,
in determining whether to continue serving another Control
ED or switching to Bulk EDs. The internal count will be
retained when crossing the frame boundary. In case of
reset, HCD is responsible for restoring this value.
0 0 = 1:1
0 1 = 2:1
1 0 = 3:1
1 1 = 4:1
PLE: PeriodicListEnable:
This bit is set to enable the processing of the periodic list
in the next Frame. If cleared by HCD, processing of the
periodic list does not occur after the next SOF. HC must
check this bit before it starts processing the list.
IE: IsochronousEnable:
This bit is used by HCD to enable/disable processing of
isochronous EDs. While processing the periodic list in a
Frame, HC checks the status of this bit when it finds an
Isochronous ED (F=1). If set (enabled), HC continues
processing the EDs. If cleared (disabled), HC halts
processing of the periodic list (which now contains only
isochronous EDs) and begins processing the Bulk/Control
lists. Setting this bit is guaranteed to take effect in the next
Frame (not the current Frame).
CLE: ControlListEnable:
This bit is set to enable the processing of the Control list in
the next Frame. If cleared by HCD, processing of the
Control list does not occur after the next SOF. HC must
check this bit whenever it determines to process the list.
When disabled, HCD may modify the list. If
HcControlCurrentED is pointing to an ED to be removed,
HCD must advance the pointer by updating
HcControlCurrentED before re-enabling processing of the
list.