DP83826E: Only negotiating to 10Mbps mode

Ross Petty

Part Number: DP83826E

I have a design with a DP83826E and am trying to use it in enhanced mode as RMII slave. When I connect it to my 1Gbps capable computer's ethernet port, it only connects at 10 Mbps mode instead of the full 100 Mbps mode. Here's an MDIO register dump:

   0x00 : 0x3100
   0x01 : 0x786D
   0x02 : 0x2000
   0x03 : 0xA131
   0x04 : 0x01E1
   0x05 : 0xCC61
   0x06 : 0x000D
   0x07 : 0x2001
   0x08 : 0x0000
   0x09 : 0x0000
   0x0A : 0x0100
   0x0B : 0x0000
   0x0C : 0x0000
   0x0D : 0x0000
   0x0E : 0x0000
   0x0F : 0x0000
   0x10 : 0x0017
   0x11 : 0x0108
   0x12 : 0x0000
   0x13 : 0x0000
   0x14 : 0x0000
   0x15 : 0x0000
   0x16 : 0x0100
   0x17 : 0x00E1
   0x18 : 0x0400
   0x19 : 0xC005
   0x1A : 0x0000
   0x1B : 0x007D
   0x1C : 0x05EE
   0x1D : 0x0000
   0x1E : 0x0002

So the surprising part of the dump is register 0x05, where bits 7, 8, and 9 are all zero, which indicates that the link partner does not advertise 100 Mbps. I don't understand why that would be the case since my PC's ethernet port works fine with higher speeds with other devices.

Any ideas on why it is defaulting to 10 Mbps?

over 2 years ago

0 Rahul over 2 years ago

TI__Expert 8721 points

Hi Ross,

Do you have a managed switch where you can connect DP83826 to and check if the link partner is actually advertising all the capabilities ?

Thanks,
Rahul

0 Ross Petty over 2 years ago

Intellectual 300 points

Hi Rahul. Unfortunately, I do not. I just know that I have connected the PC port to other devices (both 100 Mbps and 1 Gbps) and the speeds worked appropriately, so I can assume that it has the capability to advertise these speeds.

0 Rahul over 2 years ago in reply to Ross Petty

TI__Expert 8721 points

Hi Ross,

How are you determining the PHY is linking up in 10mbps ?

Regards,

Rahul

0 Ross Petty over 2 years ago in reply to Rahul

Intellectual 300 points

Multiple ways. For one, bit 1 of register 0x10 is set to 1, which means the speed status is 10 Mbps mode. Secondly, when I double click on the network adapter in Windows, it shows the speed setting as "Speed: 10 Mbps" (though it shows faster values when connected to other devices). Third, I can monitor the RMII signals on an oscope and see that they are toggling at a 5 MHz rate instead of a 50 MHz rate.

0 Rahul over 2 years ago in reply to Ross Petty

TI__Expert 8721 points

Hi Ross,

Thank you for sharing the feedback. Let me have a look at your log and update you.

Regards,
Rahul

0 Melissa Chang over 2 years ago in reply to Rahul

TI__Genius 14006 points

Hi Ross,

Ross Petty said:
I just know that I have connected the PC port to other devices (both 100 Mbps and 1 Gbps) and the speeds worked appropriately, so I can assume that it has the capability to advertise these speeds.

What other devices are you using?

Do you think you could try connecting the 826 to another 826 EVM or other EVM?

Best regards,

Melissa

0 Ross Petty over 2 years ago in reply to Melissa Chang

Intellectual 300 points

I'm referring to a standard Windows desktop computer's ethernet port, so literally anything and everything ex: raspberry pi, oscilloscopes, fpga boards. Unfortunately I do not currently have a 826 EVM.

0 Melissa Chang over 2 years ago in reply to Ross Petty

TI__Genius 14006 points

Hi Ross,

Is this your custom 826 board? Would you be able to connect to another 826 custom board or the raspberry pi?

Could you also provide a reading registers 303, 304, 305, 306, 467, 468?

Best regards,

Melissa

0 Ross Petty over 2 years ago in reply to Melissa Chang

Intellectual 300 points

   0x303 : 0x0008
   0x304 : 0x000E
   0x305 : 0x0008
   0x306 : 0x0008
   0x467 : 0x03B4
   0x468 : 0x383F

0 Melissa Chang over 2 years ago in reply to Ross Petty

TI__Genius 14006 points

Hi Ross,

Were you able to connect two custom boards together to see the results? I will take a look at your register settings and let you know if everything looks ok by tomorrow.

Best regards,

Melissa

0 Melissa Chang over 2 years ago in reply to Melissa Chang

TI__Genius 14006 points

Hi Ross,

I have reviewed your registers but nothing stands out. Are you able to connect two custom boards and let me know what speed they negotiate to?

Best regards,

Melissa

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DP83826E: Only negotiating to 10Mbps mode