STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and ...

Universal serial bus full-speed device interface (USB)
RM0008
Reception buffer address n (USB_ADDRn_RX)
Address offset: [USB_BTABLE] + n*16 + 8
USB local Address: [USB_BTABLE] + n*8 + 4
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ADDRn_RX[15:1] -
rw rw rw rw rw rw rw rw rw rw rw rw rw rw rw -
Bits 15:1 ADDRn_RX[15:1]: Reception buffer address
These bits point to the starting address of the packet buffer, which will contain the data
received by the endpoint associated with the USB_EPnR register at the next OUT/SETUP
token addressed to it.
Bit 0 This bit must always be written as ‘0’ since packet memory is word-wide and all packet buffers
must be word-aligned.
Reception byte count n (USB_COUNTn_RX)
Address offset: [USB_BTABLE] + n*16 + 12
USB local Address: [USB_BTABLE] + n*8 + 6
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
BLSIZE NUM_BLOCK[4:0] COUNTn_RX[9:0]
rw rw rw rw rw rw r r r r r r r r r r
This table location is used to store two different values, both required during packet
reception. The most significant bits contains the definition of allocated buffer size, to allow
buffer overflow detection, while the least significant part of this location is written back by the
USB peripheral at the end of reception to give the actual number of received bytes. Due to
the restrictions on the number of available bits, buffer size is represented using the number
of allocated memory blocks, where block size can be selected to choose the trade-off
between fine-granularity/small-buffer and coarse-granularity/large-buffer. The size of
allocated buffer is a part of the endpoint descriptor and it is normally defined during the
enumeration process according to its maxPacketSize parameter value (See “Universal
Serial Bus Specification”).
538/995 Doc ID 13902 Rev 9