STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and ...

USB on-the-go full-speed (OTG_FS)
RM0008
OTG_FS device endpoint-x transfer size register (OTG_FS_DIEPTSIZx)
(x = 1..3, where x = Endpoint_number)
Address offset: 0x910 + (Endpoint_number × 0x20)
Reset value: 0x0000 0000
The application must modify this register before enabling the endpoint. Once the endpoint is
enabled using the Endpoint enable bit in the Device endpoint-x control registers (EPENA bit
in OTG_FS_DIEPCTLx), the core modifies this register. The application can only read this
register once the core has cleared the Endpoint enable bit.
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
MCNT PKTCNT XFRSIZ
rw/
r/r
w
rw/
r/r
w
rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw
Bit 31 Reserved
Bits 30:29 MCNT: Multi count
For periodic IN endpoints, this field indicates the number of packets that must be transmitted
per frame on the USB. The core uses this field to calculate the data PID for isochronous IN
endpoints.
01: 1 packet
10: 2 packets
11: 3 packets
Bit 28:19 PKTCNT: Packet count
Indicates the total number of USB packets that constitute the Transfer Size amount of data for
this endpoint.
This field is decremented every time a packet (maximum size or short packet) is read from the
TxFIFO.
Bits 18:0 XFRSIZ: Transfer size
This field contains the transfer size in bytes for the current endpoint. The core only interrupts
the application after it has exhausted the transfer size amount of data. The transfer size can be
set to the maximum packet size of the endpoint, to be interrupted at the end of each packet.
The core decrements this field every time a packet from the external memory is written to the
TxFIFO.
774/995 Doc ID 13902 Rev 9