Table 230. Minimum Duration For Soft Disconnect - ST STM32F446 Series Reference Manual

RM0390
Bit 3 GONSTS: Global OUT NAK status
Bit 2 GINSTS: Global IN NAK status
Bit 1 SDIS: Soft disconnect
Bit 0 RWUSIG: Remote wakeup signaling
Table 230
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.
Operating speed
Full speed
Full speed
Full speed
High speed
0:A handshake is sent based on the FIFO status and the NAK and STALL bit settings.
1:No data is written to the Rx FIFO, irrespective of space availability. Sends a NAK
handshake on all packets, except on SETUP transactions. All isochronous OUT packets are
dropped.
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.
If LPM is enabled and the core is in the L1 (sleep) state, when the application sets this bit,
the core initiates L1 remote signaling to wake up the USB host. The application must set
this bit to instruct the core to exit the sleep state. As specified in the LPM specification, the
hardware automatically clears this bit 50 µs (T
application. The application must not set this bit when bRemoteWake from the previous
LPM transaction is zero (refer to REMWAKE bit in GLPMCFG register).
contains the minimum duration (according to device state) for which the Soft

Table 230. Minimum duration for soft disconnect

Suspended
Idle
Not Idle or suspended (Performing transactions)
Not Idle or suspended (Performing transactions)
USB on-the-go full-speed/high-speed (OTG_FS/OTG_HS)
L1DevDrvResume
Device state
RM0390 Rev 4
) after being set by the
Minimum duration
1 ms + 2.5 µs
2.5 µs
2.5 µs
125 µs
1161/1328
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