USB Host Controller
1538
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Universal Serial Bus (USB)
Table 29-4. HC Operating Mode Register (HCCONTROL) Bit Field Descriptions (continued)
Bit
Field
Value
Description
7-6
HCFS
Host controller functional state:
0
USB reset
1h
USB resume
2h
USB operational
3h
USB suspend
A transition to USB operational causes SOF generation to begin in 1 ms. The USB host controller
can automatically transition from USB suspend to USB resume if a downstream resume is received.
The USB host controller enters USB suspend after a software reset. The USB host controller enters
USB reset after a hardware reset. The USB reset state resets the root hub and causes downstream
signaling of USB reset.
5
BLE
Bulk list enable:
0
Bulk ED list not processed in the next 1-ms frame. Host controller driver can modify the list. If driver
removes the ED pointed to by the HCBULKCURRENTED from the ED list, it must update
HCBULKCURRENTED to point to an ED still on the list before it re-enables the bulk list.
1
Enables processing of bulk ED list. HCBULKHEADED must be 0 or point to a valid ED before
setting this bit. HCBULKCURRENTED must point to a valid ED or be 0 before setting this bit.
4
CLE
Control list enable:
0
Control ED list is not processed in the next 1-ms frame. Host controller driver can modify the control
ED list. If driver removes the ED pointed to by the HCCONTROLCURRENTED from the ED list, it
must update HCCONTROLCURRENTED to point to an ED still on the list before it re-enables the
control list.
1
Enables processing of the control ED list. HCCONTROLHEADED must be 0 or point to a valid ED
before setting this bit. HCCONTROLCURRENTED must be 0 or point to a valid ED before setting
this bit.
3
IE
Isochronous enable
0
Isochronous EDs are not processed. The USB host controller checks this bit every time it finds an
isochronous ED in the periodic list.
1
Enables processing of isochronous EDs. When this bit is written to 1, processing of isochronous
EDs can be enabled in the next frame, if not in the current frame.
2
PLE
Periodic list enable
0
The periodic ED lists are not processed. When written to 0, periodic list processing is disabled
beginning with the next frame.
1
Enables processing of the periodic ED lists. When written to 1, periodic list processing begins in the
next frame.
1-0
CBSR
Control/bulk service ratio. Specifies the ratio between control and bulk EDs processed in a frame.
0
One control ED per bulk ED.
1h
Two control EDs per bulk ED.
2h
Three control EDs per bulk ED.
3h
Four control EDs per bulk ED.