DP83869EVM: DP83869 MDI / MDIO pin handling for standalone working with out MCU

Hi,

I wanted to clarify some things about your setup

• Are you trying to enable 1000Base-T to 1000Base-X media converter mode? This converts copper signals at 1000
• Mbps to fiber signals at 1000Mbps
• Are you strapping the PHY into this media converter mode? The strap pins for selecting this mode are given below. If not, we must use register access to configure the PHY into this mode
• Do you have register access to the PHY thought the MDC/MDIO lines? You mentioned you tied the MDC line to a test point, is it also being used for register access? 
• What are the link partners in this test setup?

While transformerless operation is acceptable, the recommended value is 33nF, not 0.1uF, and does lead to worse EMC performance. Refer to this app note for more information

Best,

Vivaan

Hi Vivaan,

Please find the response as follows,

• Are you trying to enable 1000Base-T to 1000Base-X media converter mode? This converts copper signals at 100Mbps to fiber signals at 1000Mbps

Yes, we are trying to convert 1000 Base T from Ethernet switch to 1000 Base X. please confirm “This converts copper signals at 100Mbps to fiber signals at 1000Mbps” this is a type0 or it actually converts 100 Mbps to fiber 1000Mbps. We are interfacing the DP83869 with KSZ9477S

• Are you strapping the PHY into this media converter mode? The strap pins for selecting this mode are given below. If not, we must use register access to configure the PHY into this mode

Yes we are strapping the PHY to media converter mode as follows, please check if this is correct

• Do you have register access to the PHY thought the MDC/MDIO lines? You mentioned you tied the MDC line to a test point, is it also being used for register access? 

In our actual product we don’t have the MDC and MDIO connected to MCU. For test purpose, we can wire it to MCU and check if needed.

• What are the link partners in this test setup?

We are using KSZ9477S and SFP SMBL1G80D

We identified one problem in our schematic RX_LOS signal was not connected, We have connected RX_LOS signal from SFP to DP83869 IC along with the capacitor change, with the mentioned configuration we are trying currently

Theiv

Hi Thiev,

Theiv B said:

this is a type0 or it actually converts 100 Mbps to fiber 1000Mbps

The above is a typo. It does convert 1000Mbps Copper to 1000Mbps Fiber.

Looking at your strap pins, everything looks to be in order. The only thing that jumps out to me is the Fiber mode which is set to force mode. 

I wanted to confirm which side link are you not seeing? Is it the copper side link or the fiber side link?

Additionally, how are you verifying the link status given that MDC/MDIO lines are disconnected? It would be a good debug step to connect these so we can access the registers and look at the internal state of the PHY. The link status can be seen in register 0x01 for copper side and register 0xC01 for fiber. Please note that extended register space access would be needed for the register 0xC01. More details on this procedure can be found in this FAQ.

Could you provide a register dump for registers 0x00-0x1F, 0xC00-0xC19, and 0x6E?

Hi Thiev,

Theiv B said:

this is a type0 or it actually converts 100 Mbps to fiber 1000Mbps

The above is a typo. It does convert 1000Mbps Copper to 1000Mbps Fiber.

Looking at your strap pins, everything looks to be in order. The only thing that jumps out to me is the Fiber mode which is set to force mode. 

I wanted to confirm which side link are you not seeing? Is it the copper side link or the fiber side link?

Additionally, how are you verifying the link status given that MDC/MDIO lines are disconnected? It would be a good debug step to connect these so we can access the registers and look at the internal state of the PHY. The link status can be seen in register 0x01 for copper side and register 0xC01 for fiber. Please note that extended register space access would be needed for the register 0xC01. More details on this procedure can be found in this FAQ.

Could you provide a register dump for registers 0x00-0x1F, 0xC00-0xC19, and 0x6E?

Best,

Vivaan

Hi vivaan,

Thanks for the feedback. We have changed the Fiber mode from force mode auto negotiation. Also, Like I mentioned in the previous reply, the RX_LOS signal was connected to the DP83869. With these changes we were able to see the link up and running, We are doing additional test to check the throughput data to see if the issue is completely solved.

Will get back if some issue is still not resolved. 

Thanks,

Theiv

Hi Vivaan,

We were able to get the expected throughput as per the 1G specification. Thanks for the support. We can close this ticket.

Thanks,

Theiv