Figure 395. A-Device Hnp - ST STM32F205 series Reference Manual

RM0033
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
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
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
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
pulsing.
5. The host detects SRP from either the data-line or V
The PHY indicates V
6. The OTG_HS controller performs V
The host starts a new session by turning on V
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.
OTG core
DP
DM
DPPULLDOWN
DMPULLDOWN
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.
power-on to the device.
BUS

Figure 395. A-device HNP

1
Host
Suspend 2 4
3
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USB on-the-go high-speed (OTG_HS)
BUS
BUS
pulsing.
BUS
, indicating SRP success. The
BUS
Device
6
5
Reset Traffic
Traffic
.
BUS
BUS
discharge.
pulsing, and turns on V
Host
8
Connect
7
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BUS
.
BUS
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