ST STM32F405 Reference Manual page 1464

USB on-the-go high-speed (OTG_HS)
OTG_HS device endpoint-x interrupt register (OTG_HS_DIEPINTx) (x = 0..5,
where x = Endpoint_number)
Address offset: 0x908 + 0x20 * x
Reset value: 0x0000 0080
This register indicates the status of an endpoint with respect to USB- and AHB-related
events. It is shown in
endpoints interrupt bit of the Core interrupt register (IEPINT in OTG_HS_GINTSTS) is set.
Before the application can read this register, it must first read the device all endpoints
interrupt (OTG_HS_DAINT) register to get the exact endpoint number for the device
endpoint-x interrupt register. The application must clear the appropriate bit in this register to
clear the corresponding bits in the OTG_HS_DAINT and OTG_HS_GINTSTS registers.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
Bits 31:14 Reserved, must be kept at reset value.
Bit 13 NAK: NAK interrupt
Bit 12 Reserved, must be kept at reset value.
Bit 11 PKTDRPSTS: Packet dropped status
Bits 10:9
Bit 8 TXFIFOUDRN: Transmit Fifo Underrun (TxfifoUndrn) The core generates this interrupt when it
detects a transmit FIFO underrun condition for this endpoint.
Dependency: This interrupt is valid only when Thresholding is enabled
Bit 7 TXFE: Transmit FIFO empty
Bit 6 INEPNE: IN endpoint NAK effective
1464/1749
Figure 414. The application must read this register when the IN
Reserved
The core generates this interrupt when a NAK is transmitted or received by the device. In
case of isochronous IN endpoints the interrupt gets generated when a zero length packet is
transmitted due to unavailability of data in the Tx FIFO.
This bit indicates to the application that an ISOC OUT packet has been dropped. This bit
does not have an associated mask bit and does not generate an interrupt.
Reserved, must be kept at reset value.
This interrupt is asserted when the TxFIFO for this endpoint is either half or completely
empty. The half or completely empty status is determined by the TxFIFO empty level bit in
the Core AHB configuration register (TXFELVL bit in OTG_HS_GAHBCFG).
This bit can be cleared when the application clears the IN endpoint NAK by writing to the
CNAK bit in OTG_HS_DIEPCTLx.
This interrupt indicates that the core has sampled the NAK bit set (either by the application
or by the core). The interrupt indicates that the IN endpoint NAK bit set by the application
has taken effect in the core.
This interrupt does not guarantee that a NAK handshake is sent on the USB. A STALL bit
takes priority over a NAK bit.
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