HPA_A output signal is set to High by external pull-up resistor.
Could you teach me if output signal can be set to high without external pull-up resistor.
In that case, output level is any OK for 1.8V, 2.5V, 3.3V and 5.5V.
HPA_A and HPA_B are open drain pins. An external pull-up 1000 Ohm minimum resistor is required. The device can not drive HPA. This comes from a note in the harware guide associated with HPA_MAN_VLAUE_B bit definition and HDMI spec 1.4. A pull is required.
HPA is normally pulled up by the DDC_+5V supplied by the source. So the source determines the pull up voltage. According to the data sheet HPA Vih min = 2.6V
The ADV7842 can pull HPA low then release it high to signal the source that it should read the EDID block again. The HPA pin is usually toggles after a new EDID block has been written to the 7842.
Does HPA need to be pulled up ?
The normal connection is tDDC_5V pulls the HPA line high. When the 5V connects to sink (ADV7842) it tells the sink a connections has been made. Using the DDC_5V as a pull up source means that the receiver does not have to supply the 5V supply.
When the sink toggles the HPA line low then high, it tells the source to read the EDID data. Normally with source will not read the EDID until it sees a low to high transition.
In theory you could just supply the 5V locally if your cable doesn't have 5V on it.
HPA_A output is connected to input to external driver of 5V supply
Could you teach me register (including reserved register) for high level output because I would like to have the connection without pull-up ?
Thank you for your answer.
If there is any question about resistor, I will ask you.
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