[FAQ] DP83867IR: Packet Loss and CRC Errors with DP83867 using Short Cables

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Cecilia Reyes

Replies: 2

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Part Number: DP83867IR

Hi All,

If you are encountering an issue with packet loss or CRC errors while using the DP83867, please consider some of these items for debug when using short cables.

Short cables at 1m or less in length for your device may experience signal quality issues. One reason could be that the digital signal processing internally may take too long to converge or may even converge incorrectly at shorter lengths which could result to a bad SNR - Signal to Noise Ratio. This then creates link dropping or potential packet losses which may require you to reset your device before beginning packet transfer again. 

We have a script below that will be updated in the next revision of the DP83867 datasheet that should help eliminate any packet loss errors due to short cabling. This scripts allows for a change in the timing bandwidths to ensure the DSP converges correctly. 

ADDR	DATA	Description
0x001F	0x8000	Hard Reset
0x0053	0x2054	Threshold for consecutive amount of Idle symbols for Viterbi Idle detector to assert Idle Mode set to 5
0x00EF	0x3840	CAGC DC Compensation Disable
0x0102	0x7477	Master Training Timers - increasing time in different training states
0x0103	0x7777	Master Training Timers - increasing time in different training states
0x0104	0x4577	Master Training Timers - increasing time in different training states
0x010C	0x7777	Timing Loop Bandwidth
0x01C2	0x7FDE	Timing Loop Bandwidth
0x0115	0x5555	Slave Timers - increasing time in different training states
0x0118	0x0771	Slave Timers - increasing time in different training states
0x011D	0x6DB2	Timing Loop Bandwidth
0x011E	0x3FFB	Timing Loop Bandwidth
0x01C3	0xFFC6	Timing Loop Bandwidth
0x01C4	0x0FC2	Timing Loop Bandwidth
0x01C5	0x0FF0	Timing Loop Bandwidth
0x012C	0x0E81	FFE Fix
0x001F	0x4000	Soft Reset

If you have further questions please start a new E2E thread and our Ethernet team can clarify these items further for you.

Thanks,

Cecilia

• Ethrernet
• dp83867
• packet loss
• CRC Errors
• DP83867IR
• Short Cable

Genius 9910 points

Cecilia Reyes

• Nov 16, 2020 10:17 PM
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2 Replies

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  seokyeon kim1

  

  • Nov 17, 2020 11:29 PM

  Hi Cecilia, 

  I am the engineer who raised the above issue.

  Thank you for organizing the above issues in a credible form.

  I have an additional question, is the SNR issue for 1m applied equally to all communication frequency bands?

  Or could the length vary depending on the frequency?

  I ask a question because the wave length will vary depending on the frequency and it seems to be related to the part where the SNR becomes weak.

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• Genius 9910 points

  

  Cecilia Reyes

  

  • Nov 18, 2020 10:04 PM

  In reply to seokyeon kim1:

  Hello,

  Thanks for reading! Let's discuss on a separate thread as this seems to be an issue we can debug further.

  Thanks,

  Cecilia

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