
RM0008
USB on-the-go full-speed (OTG_FS)
Doc ID 13902 Rev 12
865/1096
contains the minimum duration (according to device state) for which the Soft
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.
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.
Bit 2
GINSTS:
Global IN NAK status
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.
Bit 1
SDIS:
Soft disconnect
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.
Bit 0
RWUSIG:
Remote wakeup signaling
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.
Table 203.
Minimum duration for soft disconnect
Operating speed
Device state
Minimum duration
Full speed
Suspended
1 ms + 2.5 µs
Full speed
Idle
2.5 µs
Full speed
Not Idle or Suspended (Performing transactions)
2.5 µs
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Reserved
FNSOF
Reserved
EE
R
R
ENUMSP
D
SUSPS
TS
r
r
r
r
r
r
r
r
r
r
r
r
r
r
r
r
r
r
Bits 31:22 Reserved
Bits 21:8
FNSOF:
Frame number of the received SOF
Bits 7:4 Reserved