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AT32F435/437
Series Reference Manual
2022.11.11
Page 420
Rev 2.03
21
Universal serial bus full-seed device
interface (OTGFS)
As a full-speed dual-role device, the OTGFS is fully compliant with the Universal Serial Bus Specification
Revision2.0.
21.1 USBFS structure
Figure 21-1 shows the block diagram of the OTGFS structure. The OTGFS module is connected to the
AHB and has a dedicated SRAM of 1280 bytes.
Figure 21-1 Block diagram of OTGFS structure
CPU
Memory
Periphe
ral 1
Periphe
ral 2
OTGFS
Data FIFO
SRAM
USB2.0 FS
USB 2.0 FS
Serial
Transceiver
USB 2.0 I/F
GPIO
21.2 OTGFS functional description
Two independent OTGFS modules are embedded in the device. The OTGFS module consists of an
OTGFS controller, PHY and 1280-byte SRAM.
The OTGFS supports control transfer, bulk transfer, interrupt transfer and synchronous transfer.
The OTGFS is a USB full-speed dual role device controller. The status of the ID line determines whether
the OTGFS acts as a host or device. When the ID line is floating, the OTGFS is used as a device. It is
used as a host while the ID line is grounded. The internal 1.5K
Ω
pull-up resistor and 1.5K
Ω
pull-down
resistor are available in the OTG PHY for the sake of dual role device.
In device mode, the OTGFS supports one bidirectional control endpoint, 7 IN endpoints, and 7 OUT
endpoints; in hose mode, the OTGFS supports 16 host channels.