Thank you for your reply. In the reference schematic, “DDCPWR” is connected to the output pin of U22, the “R0PWR5V” pin of IT6801 and the “+5V POWER” pin of HDMI interface. The "R0PWR5V" pin of the IT6801 is described in the datasheet as "TMDS transmitter detection for Port 0 (5V-tolerant)". When the HDMI input signal is connected, ①The “+5V POWER” pin of the HDMI interface will become +5V, and it seems that U22 has no meaning. ②If the “+5V POWER” pin of the HDMI interface does not have a +5V input, the U22 output seems to be a substitute. But there are two questions: Question 1: When there is no "+5V POWER" when the HDMI signal is input, does it exist? Question 2: If the situation in Question 1 exists, how does the IT6801 know that there is an HDMI signal input, so that U22 is enabled with the "ENVBUS#" signal?
As i mentioned in other thread also.. MSP430 code for this ITE card is not maintain by us.. so we do not have full understanding of the register spec for these pins. I will ask them and can give you the information latter.
But what I think this is being used for supporting the MHL mode. MHL requires to charge the device which means we have to provide additional power to the connected device (but I am not sure about that).
The HDMI detection is being done by the Hot_Plug detect pin.