DP83869HM: TDR Details

Parth Shah

Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869,

Hello,

I am designing an application to read diagnostic information such cable fault (i.e. open, short, properly terminated), MSE and SNR information. I am using DP83869 as a Media convertor mode and suing fiber cable for communication.

I am referring datasheet : https://www.ti.com/document-viewer/DP83869HM/datasheet

I can enable the TDR automatically whenever link is down through register 0x0009. I can also see registers are available for TDR from 0x180 to 0x1A6.

I need help in understanding how to calculate distance to fault, open. short or properly terminated? what are channel A to channel D and their corresponding segments? How to calculate MSE and SNE values?

Regards,

Parth Shah

over 2 years ago

0 Gerome Cacho over 2 years ago

TI__Mastermind 27915 points

Hi Parth,

I will need a few days to discuss this with the team. I expect to have an update by Tuesday of next week.

Sincerely,

Gerome

0 Parth Shah over 2 years ago in reply to Gerome Cacho

Prodigy 10 points

Hi Gerome,

Did you already discuss with team? Do you have an update?

Regards,

Parth Shah

0 Gerome Cacho over 2 years ago in reply to Parth Shah

TI__Mastermind 27915 points

Hi Parth,

I have discussed with the team, and should have an update in the very near future. Thank you for your patience.

Sincerely,

Gerome

0 Gerome Cacho over 2 years ago in reply to Gerome Cacho

TI__Mastermind 27915 points

Hi Parth,

The information required for TDR calculations has proven to be more more elusive to find. I am reaching out to internal teams regarding this matter, and hope to have a response by mid-next week. Apologies for the inconvenience. Thank you for your patience.

Sincerely,

Gerome

0 Gerome Cacho over 2 years ago in reply to Gerome Cacho

TI__Mastermind 27915 points

Hi Parth,

Please take a look at the following E2E threads.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/624167/dp83867ir-dp83867-tdr-enable?ReplyFilter=Answers&ReplySortBy=Answers&ReplySortOrder=Descending

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/825997/dp83867cr-tdr-peaks-location-calculation#pi320995=1

Specifically, the formulas listed on the second link should work on DP83869HM.

SIncerely,

Gerome

0 Parth Shah over 2 years ago in reply to Gerome Cacho

Prodigy 10 points

Hi Gerome,

Thank you for the response.

Can you help me with below information?

- What are the channels (Channel A to Channel D)?

- Please explain register 0x01A5

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/825997/dp83867cr-tdr-peaks-location-calculation#pi320995=1

- Convert Hex Value of a peak to Decimal Value(DV).

- Find the Intermediate Location (IL) = (DV x 0.8621) - 8

- Find Final Location(FL) in meters = IL + ((70 - IL) x 0.01)

Can you confirm the constants used to calculate IL are also valid for DP83869HM?

0 Gerome Cacho over 2 years ago in reply to Parth Shah

TI__Mastermind 27915 points

Hi Parth,

- What are the channels (Channel A to Channel D)?

+ Channel A-D refer to ethernet pairs seen at the RJ-45. Figure 111 of the datasheet should make this more clear.

- Please explain register 0x01A5

+ Register 0x1A5 refers to the type of cable fault that is being experienced. '1' refers to a negative peak, or a short, while '0' refers to an open

- Convert Hex Value of a peak to Decimal Value(DV)

+ Any hex to decimal calculators should be able to help with this

- Can you confirm the constants used to calculate IL are also valid for DP83869HM?

+ I would first like to clarify that the constant used for IL formula is -17 instead of -8. In addition, this is the entire formula needed to calculate the location. There is no need for FL formula as this is the only formula.

Peak_Location (m) = (DV x 0.8621)-17

Sincerely,

Gerome

0 Parth Shah over 2 years ago in reply to Gerome Cacho

Prodigy 10 points

Hi Gerome,

When you say Channel A to channel D refers to RJ45 pair, is TDR only works with RJ45?

Does TDR not work with Fiber Cables?

I have a connection as mentioned in figure 113 of datasheet.

+1 Gerome Cacho over 2 years ago in reply to Parth Shah

TI__Mastermind 27915 points

Hi Parth,

Unfortunately, TDR does not work with the Fiber side of our PHY. Only on the MDI side.

Sincerely,

Gerome

0 Parth Shah over 2 years ago in reply to Gerome Cacho

Prodigy 10 points

Hi Gerome,

Thank you for the feedback. I was looking for cable fault detection on fiber. If that is not possible, then I have to look for other solution.

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DP83869HM: TDR Details