DP83TC814S-Q1: About Cable Diagnosis function

Hi Wang,

Please note SNLA389B  is available on ti.com.

Half wire open is referring to one bus wire being open, as opposed to both bus wires being open. Peak detect is referring to a peak in the signal reflection, which indicates a fault is present on the line.

0x0310 [5:0]=0x3,  it means the fault location in 3m?

Correct.

Thanks,

David

Hi David,

1) If both bus wires open, which fault will indicate?

2) Which bit do we read when we test cable diagnosis of TC8?  0x0310  bit [8]?  bit [7]? bit [6]?

3) When DUT connects normally and cable is normally, why do we read the cable status is short?

4) When cable is normally, which register can use for indicating the cable status?

Best Regards!

Wang Jingkun

Hi David,

1) If both bus wires open, which fault will indicate?

2) Which bit do we read when we test cable diagnosis of TC8?  0x0310  bit [8]?  bit [7]? bit [6]?

3) When DUT connects normally and cable is normally, why do we read the cable status is short?

4) When cable is normally, which register can use for indicating the cable status?

Best Regards!

Wang Jingkun

Hi Jingkun,

1. If both bus wires are open, you will see open fault and half wire open bit will not be asserted.
2. You should read 0x1E to determine TDR done status, then read 0x310 bits [8:0]
3. I see a value of 0x3 in register 0x1E which means that TDR has failed. This is due to energy on the line. There must be no transmission on the line when TDR is started, from either DUT or link partner.
4. Link status is given in register 0x1 bit[2]

Thanks,

David

Hi  David,

David Creger said:

Link status is given in register 0x1 bit[2]

This is link status.  We need to know the status of cable when cable is connected normally.

Best Regards!

Wang Jingkun

Hi Jingkun,

TDR cannot be performed while normal ethernet communication is ongoing. If cable is connected normally, but energy on the line is completely quiet, TDR will show as completed with no fault detected.

Thanks,

David