ST STM32F101 series Reference Manual page 900

RM0008
OTG_FS device IN endpoint 0 transfer size register (OTG_FS_DIEPTSIZ0)
Address offset: 0x910
Reset value: 0x0000 0000
The application must modify this register before enabling endpoint 0. Once endpoint 0 is
enabled using the endpoint enable bit in the device control endpoint 0 control registers
(EPENA in OTG_FS_DIEPCTL0), the core modifies this register. The application can only
read this register once the core has cleared the Endpoint enable bit.
Nonzero endpoints use the registers for endpoints 1–3.
31 30 29 28 27 26 25 24 23 22 21
Reserved
Bits 31:21 Reserved, must be kept at reset value.
Bits 20:19 PKTCNT: Packet count
Bits 18:7 Reserved, must be kept at reset value.
Bits 6:0 XFRSIZ: Transfer size
20 19
PKTCNT
rw rw
Indicates the total number of USB packets that constitute the Transfer Size amount of data
for endpoint 0.
This field is decremented every time a packet (maximum size or short packet) is read from
the TxFIFO.
Indicates the transfer size in bytes for endpoint 0. The core interrupts the application only
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.
18 17 16 15 14 13 12 11 10
Reserved
DocID13902 Rev 15
USB on-the-go full-speed (OTG_FS)
9 8 7 6 5
rw rw rw rw rw rw rw
4 3 2 1 0
XFRSIZ
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