DP83869HM: Copper to SGMII Issue

Hi Rajesh,

Rajesh R said:

We found that register C00 always goes to 1140 instead of staying on the required 2100 (to maintain 100mbps). 

C00h [bit 13] will be affected by strap configuration.

Can you please let me know what is connected to SGMII? and what speeds does it support or is operating in?

Also, on the Link partner side connected to the RJ-45 side?

Thanks,
Rahul

Hello Rahul,

Thanks for your response. 

 We have two boards with DP chip. 

 The two boards are connected together similar to figure 9-12 of datasheet. 

 The near and far end link partners are PC’s connected to the boards in 100mbps after auto negotiation (PCs set to auto negotiation and boards also set on auto negotiation on PC side with ANEGSEL_1 pulled up to ensure board doesn’t advertise 1G speed to pc). 

 The two boards are connected together via twisted pairs. 

There are 3 link status indicators in registers 1h, 11h, and C01h. 

The first two indicators are related to board to PC link. The 3rd indicator deals with the link status at SOP/SON, SIP/SIN. 

 When we configure boards as 100M media converter; all three indicators showing link up (with register C01h showing 614D). 

 But when we configure boards as Cu-to-SGMII, only the first 2 indicators are up, while the 3rd indicator stays down (register C01h showing 6149 instead of 614D). 

 It seems as if the Cu-to-SGMII Op Mode strapping (Op Mode 1 and 2 pulled up) is forcing register C00h to stay at 1140. 

 What would be the right procedure to force SGMII register C00h to preserve the value 2100 instead of jumping to 1140 while maintaining Op Mode 1 and 2 pulled up?

 Or in other words, what is the correct procedure for a 100M Cu-to-SGMII configuration (not 1G). 

 Please note that on SOP/SON/SIP/SIN connection we are using a cable capable of 100mbps max as our project requirement states. The connection proved fine for 100baseFX but not SGMII. 

Thanking you,

Regards,

Rajesh 

Hi Rajesh,

Thank you for sharing the details.

When Link is noticed on both the MDI side, can you please share the value of Register 37h ?

Thanks,
Rahul

Hello Rahul,

Thank you for your response. 

 Register 37h showing 0000 

SGMII auto negotiation not completed. 

 Would appreciate a suggestion on what to do next. 

 I can help if you can provide me with info regarding the link establishment difference between 100baseFX block and SGMII block within the DP chip. 

Register C01 shows 614D when Op Mode 0 and 2 are pulled up (100mbps media converter mode). 

But register C01 shows 6149 when Op Mode 1 and 2 are pulled up (Cu-to-SGMII mode). 

 If we know the technical difference mentioned above, it will help in pinpointing the problem. 

 Also, in Cu-to-SGMII mode, register C00 should follow the speed of register 00h but it’s not. Why do you think?

 Thanking you,

Regards,

Rajesh 

Hi Rajesh,

Thank you for sharing your response.

Please give me some time to respond to your query as we are currently swamped with customer queries and I will update you by end of this week.

Thanks,
Rahul

Hello Rahul,

Any update on previous questions?

Waiting for your reply,

pls response ASAP it's very urgent.

Regards,

Rajesh

Hi Rajesh,

In media converter mode, C01 can be used to check the link on the fiber end and it can be used for RGMII-SGMII mode as well.

But for SGMII to Copper mode, we have to verify if SGMII auto-negotiation is completed to check if link is established, which can be verified with register 37h.

Regards,
Rahul

Hello Rahul,

Thank you for the info,

How can we make the SGMII link follow the speed of the PC link (100mbps)?

This is urgent. Your prompt response is highly appreciated. 

Regards,

Rajesh

Hi Rajesh,

The SGMII Auto-Negotiation process can be disabled and the SGMII speed mode can be forced to the MDI resolved speed. The SGMII forced speed mode can be enabled with the MDI auto-negotiation or MDI manual speed mode. SGMII Auto-Negotiation can be disabled through the SGMII_AUTONEG_EN register bit in the CFG2 register (address 14h).

Regards,
Rahul