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DP83TC812R-Q1: IOP-TDR Cable diagnostics far end short test failed

Part Number: DP83TC812R-Q1

Dear TI Team,

It is seen that certain diagnostics tests do not function as intended.

Time Domain Reflectometry:

test set:
a) after performing TDR is activated by setting bit[15] in register 0x1E
b) wait 100ms
c) readback of 0x1e = 0x3 (connected with no problem)/ 0x2(detected with problem cable short/open)
d) readback of 0x310 = 0x0(connected with no problem)/ 0xFFCX(detected cable open)/ 0xFF8X(detected cable short)

result:

near end cable (1m cable) short & open results return OK

far end cable (15m cable) open results return OK

far end cable (15m cable) short results return to be 0xFFCX(detected cable open)

attached test picture excel record: 

IOP_Cable_Diagnostics.xlsxOABR_CABLE_Far.xlsxOABR_CABLE_Near.xlsx

Regards,

Xiatian

  • Hi Rahul,

    I see the TDR Testing Procedure:

    Reg[0x0827] = 0x4800

    Reg[0x0301] = 0x1701

    Reg[0x0303] = 0x023D

    Reg[0x0305] = 0x0015,

    By doing this register value witting, the far end short cable diagnostics issue is solved.

    However, I have some questions:

    1. Some registers are written during this procedure, but in datasheet, I cannot find the register Reg[0x0827], what is its definition? May I get more data or some support files about them? It seems like only the datasheet on my hand is not enough...

    2. These registers' values are not same as datasheet reset value, should these registers' value be kept as above in formal mass production product? Or this registers value setting is only set for TDR test?

    Thank you & best regards,

    Xia Tian

  • Hi Xia Tian,

    Let me check with the internal team on the register description for 827h.

    Which other registers are you noticing other than reset values? Note that some of these registers are measurements for TDR.

    Regards,
    Rahul

  • Hi Rahul,

    Reg[0x0827] = 0x4800

    Reg[0x0301] = 0x1701

    Reg[0x0303] = 0x023D

    Reg[0x0305] = 0x0015,

    All these registers are not same as datasheet reset value, but I tried only Reg[0x0827] = 0x4800 & Reg[0x0303] = 0x023D would have refluence on TDR result...May I know for mass production, what values should put in these registers?

    Regards,

    Xia Tian

  • Hello Xia Tian,

    The register described above are internal signal processing registers and hence kept out of datasheet.

    For final screening tests, I suggest using the same sequence as mentioned in https://www.ti.com/lit/an/snla389a/snla389a.pdf

    --
    Regards,
    Gokul.

  • Hi Gokul,

    Do final screening tests mean this sequence (value in snla389a.pdf) is for tests only? For final in product, we should refer to datasheet reset value?

    Regards,

    Xia Tian

  • Hello Xia Tian,

    Sorry, I did not use the term 'final screening tests' appropriately. For using TDR functionality in final product, we should only use settings mentioned in SNLA389A and not datasheet reset/default values.

    --
    Regards,
    Gokul.

  • Hi Gokul,

    Yes, I see, as the result shows that using the settings mentioned in SNLA389A, TDR result is OK. So for the register values in final product, should also refer to the settings mentioned in SNLA389A? 

    --

    Regards,

    Xia Tian

  • Hi Xia Tian,

    That is correct.

    Regards,
    Rahul