RM0082
HS_USB2.0 host
Doc ID 018672 Rev 1
443/844
22.6.27 HcCommandStatus
register
The HcCommandStatus register is used by the Host Controller to receive commands issued
by the Host Controller Driver, as well as reflecting the current status of the Host Controller.
To the Host Controller Driver, it appears to be a "write to set" register. The Host Controller
must ensure that bits written as ‘1’ become set in the register while bits written as ‘0’ remain
unchanged in the register. The Host Controller Driver may issue multiple distinct commands
[04]
CLE
0b
R/W
R
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.
[03]
IE
0b
R/W
R
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).
[02]
PLE
0b
R/W
R
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.
[01:00]
CBSR
00b
R/W
R
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.
00 - 1:1
01 - 2:1
10 - 3:1
11 - 4:1
Table 367.
HcControl register bit assignments (continued)
Bits
Name
Reset
Read/Write
Description
HCD
HC