Texas Instruments OMAP5912 Reference Manual page 1529

Figure 55. OMAP5912 OTG Controller Response To SRP When Acting as a
Default-A Dual-Role OTG Device
VA_VBUS_OUT(max)
VA_VBUS_VLD
VBUS
VA_SESS_VLD
VB_SESS_END
GND
D+
D−
A. OTG dual-role default-B device begins discharging VBUS (optional).
B. VBUS at default-B device falls below VB_SESS_END.
C. OTG dual-role default-B device stops discharging VBUS (optional).
D. Default-B device enables SRP D+ pullup.
E. OMAP5912 OTG controller recognizes D+ pulse SRP request if D+ pulse is longer than the duration programmed in
OTG_SYSCON_2.SRP_DPW and if OTG_SYSCON_2.SRP_DATA =1. If recognized, OTG_CTRL.OTG_DRV_VBUS is
set to 1 and OPRT_CHG and SRP_DETECT interrupts are generated.
F. Default-B device disables D+ pullup (to end SRP Data Line Pulse).
G. Initial conditions for SRP are satisfied. Default-B device enables VBUS SRP pulse.
H. VBUS voltage crosses VB_SESS_END at default-B.
I. VBUS voltage crosses VA_SESS_VLD at OMAP5912 OTG transceiver. OTG transceiver issues an interrupt.
J. OMAP5912 GPIO interrupt handler identifies OTG transceiver interrupt. Handler initiates I
interrupt source information.
2
K. OMAP5912 I C operations to get transceiver interrupt source information completes. System software sees VBUS >
VA_SESS_VLD and sets OTG_CTRL.ASESSVLD to 1.
L. OMAP5912 OTG controller recognizes VBUS pulse SRP request if OTG_CTRL.ASESSVLD is 1 for longer than the
duration programmed in OTG_SYSCON_2.SRP_DPW and if OTG_SYSCON_2.SRP_VBUS=1. If recognized,
OTG_CTRL.OTG_DRV_VBUS is set to 1 and OPRT_CHG and SRP_DETECT interrupts are generated.
M. Default-B device stops driving VBUS pulse.
N. VBUS voltage discharges through various leakage sources.
O. VBUS voltage drops below VB_SESS_END at default-B device.
P. OMAP5912 OTG Interrupt handler sees OPRT_CHG interrupt and sees OTG_CTRL.OTG_DRV_VBUS set to 1 and initiates
2
I C operations to configure OTG transceiver to drive VBUS. OTG interrupt handler also sees SRP_DETECT interrupt
and begins initialization of OTG session as a default-A dual-role device.
2
Q. OMAP5912 I C operations to configure OTG transceiver to drive VBUS complete. System software writes a 1 to
OTG_CTRL.OTG_PU to indicate that the I
R. VBUS rises above VA_VBUS_VLD. OTG transceiver issues interrupt.
S. OMAP5912 GPIO interrupt handler sees OTG transceiver interrupt, initiates I
information.
T. OMAP5912 I2C operations complete. System software sees OTG status showing that VBUS voltage is above
VA_SESS_VLD and sets OTG_CTRL.ASESSVLD to 1. OMAP5912 OTG dual-role device is now ready for default-B
device to enable its pullup.
SPRU761A
A
B
F
C
D
E
2
C operation has completed.
Figure 56 shows the typical events that occur when OMAP5912 acts as an
OTG default-B dual-role device and issues an SRP to the default-A device. If
OMAP5912 completes its SRP request but the default-A device does not drive
VBUS within 5.5 seconds, the OMAP5912 OTG controller issues a
B_SRP_TIMEOUT interrupt. System software must provide a message to the
user that says the SRP request failed and that the user needs to check the
M
L
J K
N
I
H
G
2
C operations to get OTG interrupt source
Universal Serial Bus (USB)
USB OTG Controller
S T
R
Q
O
P
2
C operation to get transceiver
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