1. USB 3.2 transmission path
1.1. Transmission between USB4 host and USB4 hub
The Enhanced SuperSpeed host passes the USB 3.2 data to the USB 3.2 downstream port adapter, and then transfers the data through the USB4 port to the USB4 port of the USB4 hub, and then enters the USB 3.2 upstream port of the USB4 hub, and then enters the enhanced port of the other party. The SuperSpeed hub transmits data to the USB 3.2 downstream port, and finally outputs it to the USB4 port of the USB4 hub.
1.2. Transmission between USB4 hub and USB4 external device
The next step is to transfer data between the USB4 port of the USB4 hub and the USB4 port of the USB4 external device through the USB 3.2 downstream port adapter of the USB4 external device. Finally, it is transmitted to the location specified by the USB4 external device to realize the enhanced overspeed function. The above is the transmission path for sending and receiving USB 3.2 data.
2. DisplayPort transmission path
The DisplayPort video source is transmitted from the USB4 host through the DP input adapter to the USB4 port, and then transmitted to the upstream port of the USB4 hub, and then directly to the downstream port of the USB4 hub. This port is in turn transmitted to the USB4 upstream port of the USB4 external device. , and finally pass the video signal to the receiver through the DP output adapter, thereby realizing the display function of DisplayPort.
The above is the path for DisplayPort video sending. It can be seen from the above that the transmission of DisplpyPort does not go through any intermediate structure transfer selection, and is directly transmitted to the display device through the USB4 interface of the host, hub and external device.
3. PCIe transmission path
3.1. Transmission between USB4 host and USB4 hub
The structure composed of one uplink port and multiple downlink ports in PCIe is called a PCIe switch. The PCIe controller in the USB4 host controls the PCIe downstream port adapter to transmit data. The data is transmitted to the USB4 port of the USB4 hub through the USB4 port, then passes through the PCIe upstream port of the USB4 hub, then passes through the PCIe switch, and then passes through the PCIe downstream port, and finally transmitted to USB4 downstream port of USB4, the path to the hub is complete here.
3.2. Transmission between USB4 hub and USB4 external device
Data is transmitted through the connection path between the USB4 hub and the USB4 external device. It first passes through the PCIe upstream port adapter of the USB4 external device, and finally is transmitted to the designated location to implement the PCIe function. The above is the transmission path for sending and receiving PCIe data.
4. Transmission path between USB4 hosts
USB4 realizes data transmission between hosts, which is a function that USB 3.2 and USB 2.0 do not have. This is because USB4 adds support for the PCIe protocol. The transmission between hosts involves the structure of different layers of USB4 protocol transmission, which will be discussed later.
Data transmission is initiated from the USB4 host, then transferred or buffered by the USB4 hub, and then enters the USB4 external device to implement the corresponding function.
