hot plug detect (HPD)
Various interfaces such as High Definition Multimedia Interface(HDMI), DisplayPort, Digital Visual Interface( DVI) or PCI-Express have a control line for hot plugging.
When hot plugging is detected, a corresponding control signal, the Hot Plug Detect (HPD), is triggered. This control signal allows the receiver, which is the downstream station, to control actions of the transmitter. If a downstream station is connected, then it triggers an HPD signal. The upstream station recognizes from this that a downstream station has been connected. On the other hand, a downstream station can trigger an interrupt in an upstream device via the HPD signal.