DP83848Q-Q1: reverse polarity

Kai Nomiyama

Part Number: DP83848Q-Q1

Hi Team,

I have a question about DP83848Q-Q1 and 83849 link polarity detection and correction.

As DP83848Q-Q1 datasheet 5.5.1.3.7 Automatic Link Polarity Detection and Correction, DP8384x supports reverse polarity.
However, that comment only explains 10BASE-T reverse polarity.

Does DP8384x support 100BASE-TX reverse polarity and what register indicates phy is in reverse polarity or not in 100BASE-TX?

Regards,
Kai

over 4 years ago

0 Justin Lazaruk over 4 years ago

TI__Expert 7040 points

Hi Kai,

100Base-TX uses MLT-3 signalling and is immune to reverse polarity.

Regards,
Justin

0 Kai Nomiyama over 4 years ago in reply to Justin Lazaruk

TI__Expert 5605 points

Hi Justin,

Are there any register that we know DP83848/9 is under reverse polarity or not?

Regards,
Kai

0 Justin Lazaruk over 4 years ago in reply to Kai Nomiyama

TI__Expert 7040 points

Hi Kai,

Yes, register 0x0010[12] will give the polarity of the 10Base-T signal detected by the PHY.

Regards,
Justin

0 Kai Nomiyama over 4 years ago in reply to Justin Lazaruk

TI__Expert 5605 points

Hi Justin,

i forgot to add 100Base-TX comment.
can we apply 0x0010[12] register to 100Base-TX reverse polarity since 0x0010[12] polarity status is comment for 10Base-T in datasheet ?

Regards,
Kai

0 Justin Lazaruk over 4 years ago in reply to Kai Nomiyama

TI__Expert 7040 points

Hi Kai,

There is no register bit indicator for 100Base-TX mode, but since the MLT-3 signal is based on transitions from the previous state, the polarity of the signal does not matter.

Regards,
Justin

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DP83848Q-Q1: reverse polarity