USB systems define the following four transmission modes:
1) Control transmission
Control transmission is a bidirectional and stable transmission mode, which can be divided into three stages. The first step is a SETUP transaction from HOST to the device, which specifies the type of request to send. The second stage is data, and there are some stages that require no data; The third phase is a state that indicates that a request has successfully completed an input/output.
Control transfers take place between the application and the control endpoint of the Device via the control pipeline, and these data are analyzed by the USB device or host as defined in the format. None of the other three modes of transmission is formatted.
Control delivery has a fixed maximum packet length. This number is 64 bits in high-speed devices; This number is 8 for the low-speed device; Full speed units can be 8,16,32,64.
2) Interrupt transmission
Interrupt transfer is a polling transfer, which is a one-way transfer. The HOST will ask the interrupt end for a certain period of time. When data is transferred or can be received, it will return or transmit data, otherwise it will return NAK, indicating that it is not ready.
Although there is a certain delay, it cannot be transmitted in real time, and has a certain delay limit, and can support error resend.
At the high/high/low speed end, the maximum packet length can reach 1024/64/8.
No more than 80% of the interrupt signal can be used in microframes, and no more than 90% at full speed and low speed.
The endpoint specifier specifies the polling time for the interrupt endpoint, which can range from 1 to 255 ms, from 10 to 255 ms for the low-speed endpoint, from (2 millit val-1)*125 uS for the high-speed endpoint, and from 1 to 16 for the intermediate point.
Do you know more about wushuang usb cable now?
