The main controller serves as the data flow transmission between the host and the line to board connector equipment. These transmitted data are treated as contiguous bit streams. Each device provides one or more interfaces that can communicate with the client program. Each interface is composed of 0 or more pipelines, which transmit data between the client program and the specific terminal of the device when they separately log on. The line to board connector D establishes the interface and pipeline for the actual needs of the host software. When the equipment request is made, the master controller provides services according to the parameters provided by the host software. The line to board connector supports four basic data transmission modes: control transmission, isochronous transmission, abort transmission and data block transmission. Each transmission mode applied to the terminal with the same name has different properties.

The isochronous transmission type (or synchronous transmission) supports data transmission between peripherals and hosts with periodic, limited delay and bandwidth and constant data transmission rate. This type of error free verification can not ensure accurate data transmission and support data transmission between CTI and audio system and host. The stop transmission type supports input devices such as game controller, mouse and keyboard. The data transmission between these devices and the host computer is small and non cyclical, but they are sensitive to the response time and respond to the request immediately.

The data block transmission type supports peripherals such as printers, scanners, digital cameras, etc. these peripherals transmit a large amount of data with the host computer. The line-to-board connector can transmit this type of data only when the bandwidth is satisfied. The control transmission type supports the transmission of control, status, equipment and other information between peripherals and hosts, providing a control channel between peripherals and hosts. Each peripheral supports the control transmission type, so that equipment and command / status information can be transmitted between the host and the peripheral. The line-to-board connector adopts the block bandwidth allocation plan. If the peripheral exceeds the current bandwidth allocation or potential request, it cannot enter the device. Synchronization and termination of the transmission type of terminal save bandwidth, and ensure that the data is transmitted at a certain rate. The centralized and control terminal transmits data according to the best available bandwidth.