HPD of HDMI.

HPD (Hot Plug detection) is designed for hot swapping in a pair of HDMI connections. Simply put, when the sender accesses the receiver, the receiver responds to the HPD signal to the sender, and then the sender starts the DDC channel to read the edid information of the receiver, then perform HDCP interaction. If both parties have successfully authenticated, the video and audio will work normally. Otherwise, the connection will fail and different systems will handle the issue differently.

For example, if the edid does not support HDMI, the sender only sends video information without audio information. In this case, HDMI is only equivalent to DVI. If HDCP authentication fails, some systems may have snowflake screens and noise, and some systems will be output from high resolution (1080i, 720 p) to low resolution (480i, 480 P, HDTV is no longer a HD, but a normal SD.

An important element to proper interpretation of edid is "hot ging". The following presents a recommendation for achieving consistent results during a hot ging event.

DVI 1.0 define a HPD signal function that indicates to the host whether a monitor is connected. HPD is designed to be powered by the DDC + 5 V coming from the host, and to be independaent of whether the monitor is powered or not. in this way, a host device
Can detect the monitor and read its characteristics from edid without the monitor being powered. On a PC, this feature allows the system to load the correct display configuration without delaying the boot process.

In short, in this context, HPD serves as an indication that the edid is available to be read, however HPD may also have alternative uses. it does no imply any other state of readiness. the relevant definitions from the DVI 1.0 specification are:

A. HPD-signal is driven by monitor to enable the system to identify the presence of a monitor;

B. The monitor is required to provide a voltage of greater than + 2.4 V on the HPD pin of the connector only when the edid data structure is available to be read by the host.

Implementation notes: as an example for Hot Plug support, a simple monitor implementation of HPD support cocould be a pull up resistor to the edid power supply. after HPD goes active, the host is only expected to read edid and determine that a valid display
Mode is available and supported.

Note --- whenever the edid information in a device changes for any reason (e.g. if the edid was updated, or is capable of dynamically changing its information content), the processing device pulses HPD low for at least 100 ms. this recommendation follows
From the HDCP repeater implementation requirement that HDCP repeater pulse HPD low for at least 100 ms to indicate the connection of new device or disconnection of an existing one.

Here is just a brief discussion. We will detail the contact edid and HDCP in the future.

 

 

Connection: http://blog.csdn.net/yanzheng1113/article/details/7174513

HPD (Hot Plug detection) is designed for hot swapping in a pair of HDMI connections. Simply put, when the sender accesses the receiver, the receiver responds to the HPD signal to the sender, and then the sender starts the DDC channel to read the edid information of the receiver, then perform HDCP interaction. If both parties have successfully authenticated, the video and audio will work normally. Otherwise, the connection will fail and different systems will handle the issue differently.

For example, if the edid does not support HDMI, the sender only sends video information without audio information. In this case, HDMI is only equivalent to DVI. If HDCP authentication fails, some systems may have snowflake screens and noise, and some systems will be output from high resolution (1080i, 720 p) to low resolution (480i, 480 P, HDTV is no longer a HD, but a normal SD.

An important element to proper interpretation of edid is "hot ging". The following presents a recommendation for achieving consistent results during a hot ging event.

DVI 1.0 define a HPD signal function that indicates to the host whether a monitor is connected. HPD is designed to be powered by the DDC + 5 V coming from the host, and to be independaent of whether the monitor is powered or not. in this way, a host device
Can detect the monitor and read its characteristics from edid without the monitor being powered. On a PC, this feature allows the system to load the correct display configuration without delaying the boot process.

In short, in this context, HPD serves as an indication that the edid is available to be read, however HPD may also have alternative uses. it does no imply any other state of readiness. the relevant definitions from the DVI 1.0 specification are:

A. HPD-signal is driven by monitor to enable the system to identify the presence of a monitor;

B. The monitor is required to provide a voltage of greater than + 2.4 V on the HPD pin of the connector only when the edid data structure is available to be read by the host.

Implementation notes: as an example for Hot Plug support, a simple monitor implementation of HPD support cocould be a pull up resistor to the edid power supply. after HPD goes active, the host is only expected to read edid and determine that a valid display
Mode is available and supported.

Note --- whenever the edid information in a device changes for any reason (e.g. if the edid was updated, or is capable of dynamically changing its information content), the processing device pulses HPD low for at least 100 ms. this recommendation follows
From the HDCP repeater implementation requirement that HDCP repeater pulse HPD low for at least 100 ms to indicate the connection of new device or disconnection of an existing one.

Here is just a brief discussion. We will detail the contact edid and HDCP in the future.

 

 

Connection: http://blog.csdn.net/yanzheng1113/article/details/7174513