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DS90UB964-Q1: MAP tools questions

Sherry Liang
Genius 10255 points
Part Number: DS90UB964-Q1

Dear team,

My customer test 964 with two different cables(dacar 302 cable and RG 174 cable) using MAP tool. When the cable is 2 meters, the dacar 302 cable's result is worse than RG174 cable, which is abnormal.(Because the dacar 302 cable's performance is better than the RG 174 cable). Could you please tell me the reason?(The first picture is dacar 302, and the second picture is RG 174)

When the cable is 5 meters, the results are similar. First picture is dacar 302, and the second picture is RG 174.

In addition, now you recommend the customer to use MAP tool, in this way, they need to use the manual EQ instead of AEQ. But when the cable has been used several years, the fixed EQ value is also available for this cable?

Third question, this inface includes two parameters: EQ & SP. I can change EQ value through the register, but I don't know how to change SP because I don't find any related register. Could you please tell me how to change SP?

Thanks & Best Regards,

Sherry

  • 0
    TI__Intellectual 1930 points

    Hi Sherry,

    To address your questions:

    1. It could be that the DACAR302 cable has aged. Can your customer repeat the analysis with new cables? In addition, please check the attenuation characteristics of the two cables to see if one performs better than the other at shorter lengths.
    2. If using manual EQ, as the cable changes the EQ must be adapted. This is why we don't recommend using manual EQ for normal operation as the system will not automatically adjust for aging.
    3. I will need to look into how to adjust the SP. The reason this register is not included is because we don't allow end users to modify SP in normal operation. This is only meant for debug purposes only. Is there a reason why your customer would like to modify the SP value?

  • 0 in reply to Mostafa Shuva
    TI__Genius 10255 points

    Hi Mostafa,

    1. Ok, I will let the customer try this.

    2. So we still recommend the customer to use the AEQ, right? But the MAP tool give us the fixed EQ value. An important function of MAP tool is recommending a fixed EQ and SP to us, if we use the AEQ, what is the MAP tool used for?

    3. Maybe I have a misunderstanding about this tool. I think MAP tool give us an fixed EQ and fixed SP, and then we set the fixed EQ and fixed SP, so we not only need to use manual EQ mode, but also need to use manual SP mode. Is my understanding wrong?

    Thanks & Best Regards,

    Sherry

  • 0 in reply to Mostafa Shuva
    TI__Genius 10255 points

    Hi Mostafa,

    1. the cable the customer used is new one. And when they test the eye diagram, the DACAR302 is better than RG174 when the cable length is 2 meters.

    2. So we still recommend the customer to use the AEQ, right? But the MAP tool give us the fixed EQ value. An important function of MAP tool is recommending a fixed EQ and SP to us, if we use the AEQ, what is the MAP tool used for?

    3. Maybe I have a misunderstanding about this tool. I think MAP tool give us an fixed EQ and fixed SP, and then we set the fixed EQ and fixed SP, so we not only need to use manual EQ mode, but also need to use manual SP mode. Is my understanding wrong?

    Thanks & Best Regards,

    Sherry

  • 0 in reply to Sherry Liang
    TI__Intellectual 1930 points

    Hi Sherry,

    1. Do you know what the cable characteristics are between the two cable? It could be that the RG174 cable has better performance at shorter lengths.
    2. MAP tool is used to characterize the link margin the system has to provide a better understanding of system performance. You can also use it to debug the system to see if a different EQ/SP setting could help run the system better. TI still recommends using the AEQ for normal operation, as it will adapt with cable aging. If you only tune it manually, there's not guarantee that the EQ/SP settings will stay the same as cable ages. This is the primary goal. However, if your customer would like to manually tweak EQ/SP for their system, then they can.
    3. Your understanding is correct. Please see this app note for more information, it contains information on the registers that need to be tuned: http://www.ti.com/lit/an/snla301/snla301.pdf

    Sorry for any confusion I may have caused. :)

  • 0 in reply to Mostafa Shuva
    TI__Genius 10255 points

    Hi Mostafa,

    No matter how long or short, dacar 302 cable's performance is better than the RG 174 cable. So now customers are beginning to have some doubts about the credibility of MAP tools.

    Thanks & Best Regards,

    Sherry

  • 0 in reply to Sherry Liang
    TI__Guru* 99185 points

    Sherry,

    MAP is based on the real data capture and thus is a true performance of margin. It may be the case that at lower lengths the RG 174 has slightly better return loss which could influence the results. 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    TI__Genius 10255 points

    Hi Casey,

    This MAP tool can really replace the eye diagram, right? In the future, the customer has no need to test the eye diagram, right?

    The customer said the results tested by the MAP tool are always very good. I'm not sure whether this MAP tool can totally replace the eye diagram.

    Thanks & Best Regards,

    Sherry

  • 0 in reply to Sherry Liang
    TI__Intellectual 1930 points

    Hi Sherry,

    I would still urge the customer to do the eye diagram.