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.xlsx OABR_CABLE_Far.xlsx OABR_CABLE_Near.xlsx

Regards,

Xiatian

over 2 years ago

+1 Rahul over 2 years ago

TI__Expert 8721 points

Hi Xiatian,

Did you follow the procedure mentioned in the appnote below for TDR testing:

https://www.ti.com/lit/an/snla389a/snla389a.pdf?ts=1676051464352&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDP83TC812S-Q1

Regards,
Rahul

0 ? ? over 2 years ago in reply to Rahul

Prodigy 10 points

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

0 Rahul over 2 years ago in reply to ? ?

TI__Expert 8721 points

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

0 ? ? over 2 years ago in reply to Rahul

Prodigy 10 points

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

+1 Gokul Koraganji over 2 years ago in reply to ? ?

TI__Mastermind 19250 points

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.

0 ? ? over 2 years ago in reply to Gokul Koraganji

Prodigy 10 points

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

0 Gokul Koraganji over 2 years ago in reply to ? ?

TI__Mastermind 19250 points

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.

0 ? ? over 2 years ago in reply to Gokul Koraganji

Prodigy 10 points

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

+1 Rahul over 2 years ago in reply to ? ?

TI__Expert 8721 points

Hi Xia Tian,

That is correct.

Regards,
Rahul

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