AT32F425
Series Reference Manual
2022.03.30
Page 343
Ver 2.01
20
Universal serial bus full-seed device
interface (OTGFS)
The OTGFS software copyright is owned by Synopsys, Inc. All rights reserved. Used with permission.
As a full-speed dual-role device, the OTGFS is fully compliant with the Universal Serial Bus Specification
Revision2.0.
20.1
USBFS structure
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 20-1 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
20.2
OTGFS functional description
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 endpoints, 7 IN endpoints, and 7 OUT
endpoints; in hose mode, the OTGFS supports 16 host channels.