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Registers
20.9.7.2.1 Device Control Register (USBn_DEVCTL)
The device control register (USBn_DEVCTL) is an 8-bit register that is used to select whether the USB
controller is operating in peripheral mode or in host mode, and for controlling and monitoring the USB
VBus line. If the PHY is suspended no PHY clock is received and the VBus is not sampled. This
register is shown in
7
6
BDEVICE
FSDEV
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 20-192. Device Control Register (USBn_DEVCTL) Field Descriptions
Bit
Field
7
BDEVICE
6
FSDEV
5
LSDEV
4-3
VBUS
2
HOSTMODE
1
HOSTREQ
0
SESSION
1970
Universal Serial Bus (USB)
Preliminary
Figure 20-174
and described in
Figure 20-174. Device Control Register (USBn_DEVCTL)
5
4
LSDEV
Value
Description
This read-only bit indicates whether the USB controller is operating as the 'A' device or the 'B'
device.
0
A device
1
B device
This read-only bit is set when a full-speed or high-speed device has been detected being connected
to the port (high-speed devices are distinguished from full-speed by checking for high-speed chirps
when the device is reset). Only valid in Host mode.
This read-only bit is set when a low-speed device has been detected being connected to the port.
Only valid in Host mode.
These read-only bits encode the current VBus level as follows:
0h
Below session end
1h
Above session dnd, below AValid
2h
Above AValid, below VBusValid
3h
Above VBusValid
This read-only bit is set when the USB controller is acting as a Host.
When set, the USB controller initiates the Host negotiation when suspend mode is entered. It is
cleared when Host negotiation is completed. ('B' device only)
When operating as an 'A' device, you must set or clear this bit start or end a session. When
operating as a 'B' device, this bit is set/cleared by the USB controller when a session starts/ends.
You must also set this bit to initiate the session request protocol. When the USB controller is in
suspend mode, you may clear the bit to perform a software disconnect. A special software routine
is required to perform SRP. Details will be made available in a later document version.
© 2011, Texas Instruments Incorporated
Table
20-192.
3
2
VBUS
HOSTMODE
www.ti.com
1
0
HOSTREQ
SESSION
SPRUGX9 – 15 April 2011
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