Thunderbolt controllers multiplex one or more individual data lanes from connected PCIe and DisplayPort devices for transmission via one duplex Thunderbolt lane, then de-multiplex them for consumption by PCIe and DisplayPort devices on the other end.
|2||HPD||Hot plug detect|
|3||HS0TX+||HighSpeed transmit 0 (positive)|
|4||HS0RX+||HighSpeed receive 0 (positive)|
|5||HS0TX-||HighSpeed transmit 0 (negative)|
|6||HS0RX-||HighSpeed receive 0 (negative)|
|9||LSR2P TX||LowSpeed transmit|
|11||LSP2R RX||LowSpeed receive|
|15||HS1TX+||HighSpeed transmit 1 (positive)|
|16||HS1RX+||HighSpeed receive 1 (positive)|
|17||HS1TX-||HighSpeed transmit 1 (negative)|
|18||HS1RX-||HighSpeed receive 1 (negative)|
The Thunderbolt cable has five wires: one for management and two uni-directional pairs, one for incoming and second for outgoing traffic. The cable is a crossover cable, it swaps all receive and transmit lanes; e.g., HS1TX(P) of the source is connected to HS1RX(P) of the sink. As an active cable, it includes circuitry inside the connectors.