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4.78 OTG Device Control Register (DEVCTL)
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Registers
The OTG Device Control Register (DEVCTL) is shown in
and described in
Figure 93. OTG Device Control Register (DEVCTL)
7
6
5
4
3
2
1
0
BDEVICE
FSDEV
LSDEV
VBUS
HOSTMODE
HOSTREQ
SESSION
R-0
R-0
R-0
R-0
R-0
R/W-0
R/W-0
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 94. OTG Device Control Register (DEVCTL) Field Descriptions
Bit
Field
Value
Description
7
BDEVICE
This read-only bit indicates whether the USB controller is operating as the 'A' device or the 'B'
device.
device.
0
'A' device
1
'B' device
Only valid while a session is in progress.
6
FSDEV
0-1
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.
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.
5
LSDEV
0-1
This read-only bit is set when a low-speed device has been detected being connected to the port.
Only valid in Host mode.
Only valid in Host mode.
4-3
VBUS
0-3h
These read-only bits encode the current VBus level as follows:
0
Below Session End
1h
Above Session End, below AValid
2h
Above AValid, below VBusValid
3h
Above VBusValid
2
HOSTMODE
0-1
This read-only bit is set when the USB controller is acting as a Host.
1
HOSTREQ
0-1
When set, the USB controller will initiate the Host Negotiation when Suspend mode is entered. It is
cleared when Host Negotiation is completed. ('B' device only)
cleared when Host Negotiation is completed. ('B' device only)
0
SESSION
0-1
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.
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.
SPRUGH3 – November 2008
Universal Serial Bus (USB) Controller
137