4.9.4. USB3.1 Type-C Interface
A USB3.1 Type-C interface (J8) is provided on the PCIe* bracket. The interface supports SuperSpeed up to 10 Gbps as well as the backward compatible support of USB2.0.
The Type-C connector provides any orientation insertion of the cable. To support this feature, a Texas Instruments DRP port Controller and SuperSpeed 2:1 MUX HD3SS3220 is used. The port is configured in DRP mode. The controller detects the orientation of the plugged cable and multiplexes the transceiver of the FPGA to two SuperSpeed interfaces. It also determines if the port is an Upstream Facing Port (UFP) or a Downstream Facing Port (DFP). It controls the power switch to feed the power to cable when in DFP mode. HD3SS3220 is controlled by the FPGA through a dedicated I2C bus.
Parameters of USB3.1
- I2C address is 7'b110_0111 by default. It can be changed to 7'b100_0111 by installing R199 and removing R198
- Port mode is Dual Role Port (DRP) by default. It can be chnaged to DFP if R177 is installed, or UFP if R178 is installed.
- Current Advertisement is 1.5A
- EQ for channel 1: 5.5 dB
- EQ for channel 2: 5.5 dB
- VOD Gain: 0 for both channels with linear range 1200 mV.
The resistors are set in pull down mode on the board. Other configurations are available by changing the pulling resistors. EQ configurations with pin level "1" are not available.
The power of USB VBUS is controlled with a Texas Instruments power switch TPS25910. The voltage is 5 V and the maximum current is 1.5 A. The power control pin to the TPS25910 is connected to the USB_ID output of HD3SS3220. The power is applied to VBUS only when the port is in DFP mode. The power application can be controlled by the FPGA too. The USB_PWEN signal is active high because of the NMOS inverter.
USB_ID pin on HD3SS3220 indicates the port is linked as a power source (DFP), or dual-role (DRP) acting as source (DFP). USB_ID is connected to the FPGA as well as TPS25910 and USB3320.
Backward support for USB2.0 is implemented with Microchip's USB3320 USB PHY. It interfaces with the FPGA through ULPI interface. The reference clock mode for ULPI is FPGA clock output to USB3320.
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