ST STM32L4x6 Reference Manual page 1602

USB on-the-go full-speed (OTG_FS)
The application is expected to write the requests as and when the Request queue space is
available and until the XFRC interrupt is received.
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Bulk and control IN transactions
A typical bulk or control IN pipelined transaction-level operation is shown in
See channel 2 (ch_2). The assumptions are:
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1602/1693
The application is attempting to receive two maximum-packet-size packets
(transfer size = 1 024 bytes).
The receive FIFO can contain at least one maximum-packet-size packet and two
status Words per packet (72 bytes for FS).
The non-periodic request queue depth = 4.
DocID024597 Rev 3
RM0351
Figure 505.