Texas Instruments OMAP5912 Reference Manual page 1333

Table 20. HC Root Hub A Register (HCRHDESCRIPTORA)
Bit Name
31:24 POTPG
23:13 Reserved
12 NOCP
SPRU761A
The HC root hub A register defines several aspects of the USB host controller
root hub functionality.
Value Description
Power-on to power-good time
This field defines the minimum amount of time (2 ms ×
POTPG) between the USB host controller turning on
power to a downstream port and when the USB host
can access the downstream device.
This field has no effect on USB host controller
operation. After turning on power to a port, the USB
host controller driver must delay the amount of time
implied by POTPG before attempting to reset an
attached downstream device.
The required amount of time is implementation-specific
and must be calculated based on the amount of time
the VBUS supply takes to provide valid VBUS to a
worst-case downstream USB function controller.
The implementation-specific value must be computed
and then written to this register before the USB host
controller driver is initialized.
Because OMAP5912 does not provide a direct control
from the USB host controller to switch VBUS on and
off, this value must take into account any delays
caused by other methods of controlling VBUS
externally.
This bit has no relationship to the OTG controller
register bits that relate to VBUS. System software can
update this register to simplify host controller driver
and/or OTG driver coding.
Reserved
No overcurrent protection
When 1, this bit indicates that the USB host controller
does not implement overcurrent protection inputs.
OMAP5912 does not provide signals to allow
connection of external overcurrent indication signals to
the USB host controller, so this bit defaults to 1.
This bit has no relationship to the OTG controller
register bits that relate to VBUS.
USB Host Controller
Type
R/W
R/W
Universal Serial Bus (USB)
Reset
0xA
1
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