Texas Instruments OMAP5912 Reference Manual page 1511

Table 69. OTG Interrupt StatusRegister (OTG_IRQ_SRC)
Bit Name
15 DRIVER_SWITCH
14 Reserved
13 A_VBUS_ERR
SPRU761A
Description
Driver switch interrupt status. This bit reflects the status of the driver
switch interrupt source. Driver switch interrupts occur when HNP
completes and control of the OTG link must switch between the
OMAP5912 USB host controller driver and the OMAP5912 USB device
controller driver (or vice versa).This interrupt also occurs upon enabling
the OTG functionality by writing OTG_SYSCON_2.OTG_EN = 1. In this
case, OGT_CTRL.DRIVER_SEL selects the controller driver that is
appropriate, given the value of OTG_CTRL.ID.
0: Driver switch interrupt is inactive.
1: Driver switch interrupt is active.
This bit is cleared either by writing a 1 or by soft reset or hardware reset.
This bit has no effect when OTG_SYSCON_2.OTG_EN is 0.
Reserved
A-device Vbus error interrupt status. This bit reflects the status of the
A_VBUS_ERR interrupt. VBUS errors occur when the OMAP5912 OTG
controller state machine acts as a default-A dual-role device and
transitions into state A_VBUS_ERR. Usually, the state machine
transitions into state A_VBUS_ERR if VBUS voltage drops below the
A_VBUS_VALID threshold because of low battery conditions or heavy
loading by the attached device. Transitions into this state can
unintentionally occur if system software turns off VBUS power and writes
0 to OTG_CTRL.VBUSVLD before writing 1 to OTG_CTRL.OTG
_BUS_DROP. Writing 1 to OTG_CTRL.OTG_BUS_DROP clears the
source of this interrupt.
0: VBUS error interrupt is inactive.
1:VBUS error interrupt is active.
This bit is cleared either by writing a 1 or by soft reset or hardware reset.
This bit has no effect when OTG_SYSCON_2.OTG_EN is 0.
USB OTG Controller
Universal Serial Bus (USB) 219