Table 176. Minimum Duration For Soft Disconnect - ST STM32F40 Series Reference Manual

USB on-the-go full-speed (OTG_FS)
Bit 2 GINSTS: Global IN NAK status
Bit 1 SDIS: Soft disconnect
Bit 0 RWUSIG: Remote wakeup signaling
Table 176
disconnect (SDIS) bit must be set for the USB host to detect a device disconnect. To
accommodate clock jitter, it is recommended that the application add some extra delay to
the specified minimum duration.

Table 176. Minimum duration for soft disconnect

Operating speed
Full speed
Full speed
Full speed
OTG_FS device status register (OTG_FS_DSTS)
Address offset: 0x808
Reset value: 0x0000 0010
This register indicates the status of the core with respect to USB-related events. It must be
read on interrupts from the device all interrupts (OTG_FS_DAINT) register.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
Reserved
Bits 31:22 Reserved, must be kept at reset value.
Bits 21:8 FNSOF: Frame number of the received SOF
Bits 7:4 Reserved, must be kept at reset value.
1085/1422
0: A handshake is sent out based on the data availability in the transmit FIFO.
1: A NAK handshake is sent out on all non-periodic IN endpoints, irrespective of the data
availability in the transmit FIFO.
The application uses this bit to signal the USB OTG core to perform a soft disconnect. As
long as this bit is set, the host does not see that the device is connected, and the device
does not receive signals on the USB. The core stays in the disconnected state until the
application clears this bit.
0: Normal operation. When this bit is cleared after a soft disconnect, the core generates a
device connect event to the USB host. When the device is reconnected, the USB host
restarts device enumeration.
1: The core generates a device disconnect event to the USB host.
When the application sets this bit, the core initiates remote signaling to wake up the USB
host. The application must set this bit to instruct the core to exit the Suspend state. As
specified in the USB 2.0 specification, the application must clear this bit 1 ms to 15 ms after
setting it.
contains the minimum duration (according to device state) for which the Soft
Suspended
Idle
Not Idle or Suspended (Performing transactions)
r r r
Doc ID 018909 Rev 4
Device state
FNSOF
r r r r r r r
Minimum duration
1 ms + 2.5 µs
2.5 µs
2.5 µs
9 8 7 6 5
Reserved
r r r r
RM0090
4 3 2 1 0
r r r r