DP83TC811-Q1: Link Failure

Hi Charles-san,

Thank you for your reply.

> Register: 0x0000 (BMCR)
> 0x3100 (Speed Select=100Mbps, Auto-Negotiation Enable, Full-Duplex) à  Link OK
> 0x2100 (Speed Select=100Mbps, Auto-Negotiation Disable, Full-Duplex) à Link Fail

The above is the register of DP83TC811.  This setting is described in the data sheet 7.6.2 as follows.

I have not heard why the customer is turning off auto-negotiation on the DP83822. I'll check it.

I think register 0x0019 [15] =0 is a DP83822 register. 

1) Please let me confirm, should we set register 0x0019 [15] =1 of DP83822 when using Auto-Negotiation?

2) Does TI recommend using auto-negotiation because it helps converge link functions with link partners?

3) This is the first question. The customer assumes that both the DT83TC811 and DP83822 should be linked at 100M because the auto-negotiation of the bothe ICs are OFF. However they saw the two ICs can't be linked. Is the phenomenon that the two ICs can't be linked is right behavior in this case?

Regarding why the customer is considering the DT83TC811, the customer plans to develop a system that can connect a regular LAN and an in-car LAN, and use the system to develop and debug in-car networks. And also because it is also used in the DP83TC811EVM. They are planning to develop something exactly like DP83TC811EVM.

I would appreciate it if you reply to the above three questions.

Thanks ＆ Regards,
T.Imai

Hi Imai-San,

Let me check in with my team. I'll have a response by end of day on Thursday.

Best,

Charles

Hi Charles-san,

Thank you. I am looking forwad to hearing from you on Thursday, in Japan on Friday.

Best Regards,

T.Imai

Hi Imai-San,

Lets take a step back. DP83TC811EVM should work out of the box. No registers should be written on the PHYs. 

1. Please ensure one DP83TC811 is set to slave mode, and the other DP83TC811 is set to master mode. 

2. Please ensure both DP83TC811 are set to autonomous mode. 

3. Please read out register 0x0001 on DP83822 and DP83TC811 when both DP83TC811EVMs are connected. 

Best,

Charles

Hi Charles-san,

Thank you for your quick response. I informed your reply to the customer and asked them to answer to your three questions.

Do you need information about your three new questions to answer the customer question? If not, please reply as soon as possible.

Thanks & Regards,

T.Imai

Hi Imai-san,

Charles said:

1. Please ensure one DP83TC811 is set to slave mode, and the other DP83TC811 is set to master mode. 

2. Please ensure both DP83TC811 are set to autonomous mode. 

3. Please read out register 0x0001 on DP83822 and DP83TC811 when both DP83TC811EVMs are connected. 

Point 1 and 2 are not questions. They are actions customer should take to solve EVM no link-up issue.

Customer should answer question and tell you what data is in register 0x0001.

Best,

Charles

Hi Charles-san,

Thank you for the explanation. I received the following reply from the customer.

1)Yes, one DP83TC811 is set to slave mode, and the other DP83TC811 is set to master mode. 

2)The link fails between PC and the DP83TC811.
     When the auto-negotiation of the board is ON, the link succeed whether the auto-negotiation of the NIC of the PC is ON or OFF.
     When the auto-negotiation of the board is OFF, the link fails whether the auto-negotiation of the NIC of the PC is ON or OFF.

3)The value of address 0x0001 of the DP83TC811 is,  when link succseeded : 0x786D,   when Link failed  : 0x7849.

    The value of address 0x0001 of the DP83822 is, when link succeeded : 0x0061,  when link failed : 0x0061

The customer is evaluating the system with the following configuration.

PC ― DP83TC811EVM ― DP83TC811EVM ― PC,  with using USB-2-MDIO.

If the customer tries to communicate at 100Mbps from a PC, the link fails. Could you please tell us if this is normal behavior?

Best Regards,

T.Imai

Hi Imai-san,

Takashi Imai said:

3)The value of address 0x0001 of the DP83TC811 is,  when link succseeded : 0x786D,   when Link failed  : 0x7849.

    The value of address 0x0001 of the DP83822 is, when link succeeded : 0x0061,  when link failed : 0x0061

I believe you have the devices flipped. Read 0x0061 should correspond with DP83TC811. Am I correct in this assumption? 

I will give advice based on this assumption : 

The value of address 0x0001 of the DP83822 is,  when link succeeded : 0x786D,   when Link failed  : 0x7849.

The value of address 0x0001 of the DP83TC811 is, when link succeeded : 0x0061,  when link failed : 0x0061

From above register, DP83TC811 never links up. For correct link-up, we expect DP83TC811 device register 0x0001 = 0x0065.

Please have customer check if this is the configuration of the EVMs: 

Best,

Charles

Hi Charles-san,

This is just an update. The customer replied that the values of DP83TC811 and DP83822 were reversed.

Therefore, the link failure occurs on the DP83822 side, and it occurs when the DP83822 link is set to auto-negotiation OFF.

The 0x0001 register of the DP83TC811 is the value of 0x0065 when link is ok.

I am checking if the customer has any additional questions. I will let you know the result.

Thanks & Regards,
T.Imai

Hi Imai-san,

Thanks for the update. I'll keep this thread open for now. 

Best,

Charles

Hi Charles-san,

I received new inquiry from the customer about link between DP83822 abd their PC.

The customer informed me that the link between the PC and the DP83822 on the DP83TC811EVM is possible when the auto-nego of the DP83822 is set to OFF (bit 12 of the 0x0000 register =1), but not when it is set to 0. Is this behavior expected?

Thanks ＆Regards,
T.Imai

Hi Charles-san,