SFP Link status polling via I2C

[paulleons90]

Hello,

I am trying to read the status of SFP port using I2C interface for FTLX1471D3BTL. I use optical fiber to connect between the
NIC card and the SFP module. I am trying to see if the link between the NIC card and the SFP module is up or not and I have 2 main problems:

1. I am unable to find a register in the register map of I2C slave which gives status of link up. In the address 110, I can read the state of RX_LOS_State which gives information if the cable is physically plugged in or not. But it do not provide any information if the link is up or not.
2. I read this register address 110 using an I2C interface. After the transaction is completed, the link is down. I have to do a reset to the slave device to bring the link back up. What is the cause of this problem and how can I fix it?

Any help is greatly appreciated.

Thanks,
Paul

 

[Dan Mills]

I always thought a SFP was a physical link layer only device?
If so you need to ask the PHY or MAC rather then the SFP for link status, the SFP will only tell you that it sees modulated light, not that the light encodes ethernet frames.

The SFP modules I have played with output a PECL pair that is pretty much an amplified and limited version of the signal from the photodiode, you want the PHY or MAC levels to give you link status, the SFP does not decode things that far.

Regards, Dan.