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M451
May. 4, 2018
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Rev.2.08
M4
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[2]
PLE
Periodic List Enable Bit
When set, this bit enables processing of the Periodic (interrupt and isochronous) list. The
Host Controller checks this bit prior to attempting any periodic transfers in a frame.
0 = Processing of the Periodic (Interrupt and Isochronous) list after next SOF (Start-Of-
Frame) Disabled.
1 = Processing of the Periodic (Interrupt and Isochronous) list in the next frame Enabled.
Note:
To enable the processing of the Isochronous list, user has to set both PLE and IE
(HcControl[3]) high.
[1:0]
CBSR
Control Bulk Service Ratio
This specifies the service ratio between Control and Bulk EDs. Before processing any of
the non-periodic 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.
00 = Number of Control EDs over Bulk EDs served is 1:1.
01 = Number of Control EDs over Bulk EDs served is 2:1.
10 = Number of Control EDs over Bulk EDs served is 3:1.
11 = Number of Control EDs over Bulk EDs served is 4:1.