TMDS181: TMDS181 in Sink Side questions

Hello Masazumi

I send you the answer of your questions.

Q１
PIN：HDP_SNK, SDA_SNK, SCL_SNK, SDA_SRC, SCL_SRC
VCC,VDD=0V
At this time, is it OK to apply the signal to the HDP_SNK, SDA_SNK, SCL_SNK, SDA_SRC, SCL_SRC pin?

No, this device is not designed for this kind of use.

Q2
datasheetP43、P44.
Figure 35.36 TMDS181 in Sink Side Application
The SCL_SRC and SDA_SRC pins are not connected, but are there any reasons?

As sources are not consistent in implementing all aspects of the DDC link, TI recommends doing this connection

Q3
We are thinking about use at the sink.
In the design, connectors and devices should be mounted on the same surface.
At this time, do I need to use Retimer mode only with I2C control?

This is the best option for sink side application.

Q4
　　10 – Automatic retimer when HDMI2.0a based upon
　　11 – Retimer mode across full range 250 Mbps to 6 Gbps
What is the difference between the two modes?

　10 – Automatic retimer when HDMI2.0a based upon
In this case, the device is in automatic configuration based upon TMDS_CLOCK_RATIO_STATUS when is in HDMI2.0, it means that the device will work from 3.4 Gbps to 6 Gbps, the TMDS clock is in 1/40 of TMDS bit period

　11 – Retimer mode across full range 250 Mbps to 6 Gbps
In this case, you will have the retimer mode from 250 Mbps to 6 Gbps. In this mode when changing crossover point, need to toggle PD_EN or toggle external HPD_SNK

Q5
When using Retimer mode, do you need to control PD_EN or HPD_SNK at the crossover point?
Yes
Is the crossover point at that time 1.0 Gbps or 3.4 Gbps?

from .75 Gbps to 1.25 Gbps with crossover frequency hysteresis 250 MHz

Regards
Francisco

Hello Masazumi

I send you the answer of your questions.

Are there any mistakes in the procedure?
Do you only want to swap the lanes? if so, you can configure the device in retimer and redriver mode, if you also want to use the polarity swap, you have to have the device in retimer mode. In your procedure looks like you have the device in I2C mode if so, you have to write directly to the register to activate this option. If you are using GPIO mode, then you have to use the SWAP/POL pin as you say. Please, take a look at the 09 register

When swapping lanes and polarities, please tell me the order of setting.
You only have to have the device in retimer mode and activate it through the mode that you are using.

Is TMDS 181 correspondence replacing only one side of lane and polarity?
（Is it impossible to exchange both?）
Yes, it is impossible. This device is designed only for the receiver side.

１ I am thinking of the connection in the above figure.
Is it feasible?
Yes, it is possible.

２ If it is possible, is there anything you need to be aware of, such as the control setting order?
Yes, it is possible. You only have to consider in which mode are you working.

Can I set the ReTimer setting and SWAP setting at the same time?
No, it is not possible.

Also, do you need control of HPD etc at that time?
You have to have first the HPD enabled and then, continue with the correct programation.

３ Is it possible to think that the output pins are the same even if swap setting of lane and polarity is done?
（As for polarity swap, since it is unknown what happens to output polarity, it confirms.）
It is not possible, you can check this one directly on the lanes.

４ Set 1: 0 of 0 Ah to "10". Is it possible to swap both lanes and polarities in all bands?
Yes, it is.

５ When 1: 0 of 0 Ah is set to "11",
it is possible to think that there is no crossover point and operation of HPD or PD is unnecessary because all bands become Retimer operation?
This question is not clear to me.

６ In the connection diagram of data sheet P23-44, SDA_SNK and SCL_SNK are directly connected to the Rx connector.
In EVM, 5V is applied to SDA_SNK and SCL_SNK if the HDMI cable is connected even if TMDS181 is not turned on.
Even with other equipment, I think voltage will be applied if you connect the HDMI cable.
Therefore, should I connect the SDA_SNK, SCL_SNK pins directly to the connector?
Yes, it has to be connected. You have to see that this is a sink application (take a look at Pull-up values and connections).


７ If SDA_SRC, SCL_SRC is not used, please tell me why to connect SDA_SNK, SCL_SNK to the DDC line.
I am guessing that you are talking about of the sink side application, if so, as sources are not consistent in implementing all aspects of the DDC link, TI recommends to configure the TMDS181 as per Figure on the datasheet.

Please, let me know if you need something else.

Regards
Francisco