ST STM32F412 Reference Manual page 1039

RM0402
Bits 31:19 Reserved, must be kept at reset value.
Bit 18 DSBESLRJCT: Deep sleep BESL reject
Bits 17:12 Reserved, must be kept at reset value.
Bit 11 POPRGDNE: Power-on programming done
Bit 10 CGONAK: Clear global OUT NAK
Bit 9 SGONAK: Set global OUT NAK
Bit 8 CGINAK: Clear global IN NAK
Bit 7 SGINAK: Set global IN NAK
Bits 6:4 TCTL[2:0]: Test control
Bit 3 GONSTS: Global OUT NAK status
Core rejects LPM request with BESL value greater than BESL threshold programmed.
NYET response is sent for LPM tokens with BESL value greater than BESL threshold. By
default, the deep sleep BESL reject feature is disabled.
The application uses this bit to indicate that register programming is completed after a
wakeup from power down mode.
Writing 1 to this field clears the Global OUT NAK.
Writing 1 to this field sets the Global OUT NAK.
The application uses this bit to send a NAK handshake on all OUT endpoints.
The application must set the this bit only after making sure that the Global OUT NAK
effective bit in the core interrupt register (GONAKEFF bit in OTG_GINTSTS) is cleared.
Writing 1 to this field clears the Global IN NAK.
Writing 1 to this field sets the Global non-periodic IN NAK.The application uses this bit to
send a NAK handshake on all non-periodic IN endpoints.
The application must set this bit only after making sure that the Global IN NAK effective bit
in the core interrupt register (GINAKEFF bit in OTG_GINTSTS) is cleared.
000: Test mode disabled
001: Test_J mode
010: Test_K mode
011: Test_SE0_NAK mode
100: Test_Packet mode
101: Test_Force_Enable
Others: Reserved
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.
USB on-the-go full-speed (OTG_FS)
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