USB on-the-go high-speed (OTG_HS)
RM0090
1526/1731
DocID018909 Rev 11
1.
To save power, the host suspends and turns off port power when the bus is idle.
The OTG_HS controller sets the early suspend bit in the Core interrupt register after 3
ms of bus idleness. Following this, the OTG_HS controller sets the USB suspend bit in
the Core interrupt register.
The OTG_HS controller informs the PHY to discharge V
BUS
.
2. The PHY indicates the session’s end to the device. This is the initial condition for SRP.
The OTG_HS controller requires 2 ms of SE0 before initiating SRP.
For a USB 1.1 full-speed serial transceiver, the application must wait until V
BUS
discharges to 0.2 V after BSVLD (in OTG_HS_GOTGCTL) is deasserted. This
discharge time can be obtained from the transceiver vendor and varies from one
transceiver to another.
3. The USB OTG core informs the PHY to speed up V
BUS
discharge.
4. The
application
initiates SRP by writing the session request bit in the OTG Control and
status register. The OTG_HS controller perform data-line pulsing followed by V
BUS
pulsing.
5. The host detects SRP from either the data-line or V
BUS
pulsing, and turns on V
BUS
.
The PHY indicates V
BUS
power-on to the device.
6. The OTG_HS controller performs V
BUS
pulsing.
The host starts a new session by turning on V
BUS
, indicating SRP success. The
OTG_HS controller interrupts the application by setting the session request success
status change bit in the OTG interrupt status register. The application reads the session
request success bit in the OTG control and status register.
7. When the USB is powered, the OTG_HS controller connects, completing the SRP
process.
A-device host negotiation protocol
HNP switches the USB host role from the A-device to the B-device. The application must set
the HNP-capable bit in the Core USB configuration register to enable the OTG_HS
controller to perform HNP as an A-device.
Figure 430. A-device HNP
1. DPPULLDOWN = signal from core to PHY to enable/disable the pull-down on the DP line inside the PHY.
DMPULLDOWN = signal from core to PHY to enable/disable the pull-down on the DM line inside the PHY.
a
i156
83
b
OTG core
DP
DM
DPPULLDOWN
DMPULLDOWN
Ho
s
t
Device
Ho
s
t
1
Sus
pend 2
3
4
5
Re
s
et
6
Tr
a
ffic
7
8
Connect
Tr
a
ffic