STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and ...

RM0008
USB on-the-go full-speed (OTG_FS)
Bit 17 NAKSTS: NAK status
It indicates the following:
0: The core is transmitting non-NAK handshakes based on the FIFO status.
1: The core is transmitting NAK handshakes on this endpoint.
When either the application or the core sets this bit:
For non-isochronous IN endpoints: The core stops transmitting any data on an IN endpoint,
even if there are data available in the TxFIFO.
For isochronous IN endpoints: The core sends out a zero-length data packet, even if there
are data available in the TxFIFO.
Irrespective of this bit’s setting, the core always responds to SETUP data packets with an ACK
handshake.
Bit 16 EONUM: Even/odd frame
Applies to isochronous IN endpoints only.
Indicates the frame number in which the core transmits/receives isochronous data for this
endpoint. The application must program the even/odd frame number in which it intends to
transmit/receive isochronous data for this endpoint using the SEVNFRM and SODDFRM
fields in this register.
0: Even frame
1: Odd frame
DPID: Endpoint data PID
Applies to interrupt/bulk IN endpoints only.
Contains the PID of the packet to be received or transmitted on this endpoint. The
application must program the PID of the first packet to be received or transmitted on this
endpoint, after the endpoint is activated. The application uses the SD0PID register field to
program either DATA0 or DATA1 PID.
0: DATA0
1: DATA1
Bit 15 USBAEP: USB active endpoint
Indicates whether this endpoint is active in the current configuration and interface. The core
clears this bit for all endpoints (other than EP 0) after detecting a USB reset. After receiving
the SetConfiguration and SetInterface commands, the application must program endpoint
registers accordingly and set this bit.
Bits 14:11 Reserved
Bits 10:0 MPSIZ: Maximum packet size
The application must program this field with the maximum packet size for the current logical
endpoint. This value is in bytes.
Doc ID 13902 Rev 9 765/995