Figure 493. Otg Full-Speed Block Diagram; Usb Otg Functional Description - ST STM32L4x6 Reference Manual

USB on-the-go full-speed (OTG_FS)
43.4

USB OTG functional description

43.4.1 USB OTG block diagram
43.4.2 OTG core
The USB OTG receives the 48 MHz ±0.25% clock from the reset and clock controller
(RCC), via an external quartz. The USB clock is used for driving the 48 MHz domain at full-
speed (12 Mbit/s) and must be enabled prior to configuring the OTG core.
The CPU reads and writes from/to the OTG core registers through the AHB peripheral bus.
It is informed of USB events through the single USB OTG interrupt line described in
Section 43.13: OTG_FS
The CPU submits data over the USB by writing 32-bit words to dedicated OTG locations
(push registers). The data are then automatically stored into Tx-data FIFOs configured
within the USB data RAM. There is one Tx FIFO push register for each in-endpoint
(peripheral mode) or out-channel (host mode).
The CPU receives the data from the USB by reading 32-bit words from dedicated OTG
addresses (pop registers). The data are then automatically retrieved from a shared Rx FIFO
configured within the 1.25 KB USB data RAM. There is one Rx FIFO pop register for each
out-endpoint or in-channel.
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Figure 493. OTG full-speed block diagram

interrupts.
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