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Gigabit ethernet on the SLK2511

Andrew Cottrell
Prodigy 100 points
Other Parts Discussed in Thread: TLK2201B, TLK1221

Hello

On the datasheet for the SLK2511 it states under a feature that it is capable of Gigabit Ethernet

However there is no other mention of it at all in the datasheet. 

Is the device actually capable of this? Is it possible to get more information on this functionality?

How do we enable this mode? I assume you do it with auto rate detection, but then what are the outputs of rate sel?

Cheers,

Andy

  • 0
    TI__Mastermind 20820 points

    Hi Andrew,


    This is strange to me as well please allow me some time to look into this for you.

    Regards,

    Michael Peffers

    High Speed Interface Applications

  • 0 in reply to Michael Peffers
    Prodigy 100 points

    Great, glad someone's looking into it now. I had been trying other methods of communication for a while.

    We've got this going into a design currently where GbE is a nice feature we would like to have.

    Cheers

    Andy

  • 0 in reply to Andrew Cottrell
    TI__Mastermind 20820 points

    Hi Andrew,

    The SLK2511 is not a GbE device because it does not have any of the coding layer needed for true GbE. We simply support the GbE data rate, to truly pass GbE data through this device their would have to be an intermediate block between the SLK2511 and the GbE data source to convert the interface for you.

    We do offer the TLK1121 and the TLK2201B which are GbE true devices, would these be something that you are interested in?

    Regards,

    Michael Peffers

    High Speed Interface Applications

  • 0 in reply to Michael Peffers
    Prodigy 100 points

    Hi Michael

    Thanks for looking into this.

    We're still going to use the SLK2511 in our design, GbE would have just been a nice additional feature, but wasnt a hard requirement.

    What sort of intermediate block would we require for GbE? 

    What happens if GbE ends up on the line interface for the device? 

    Thank you

    Andrew

  • 0 in reply to Andrew Cottrell
    TI__Mastermind 20820 points

    Hi Andrew,

    The intermediate block would be a device that could take a 10bit parallel interface that is 8b/10b encoded, which is standard in GbE, and convert it into a 4 lane GbE serial link to be read into the SLK2511. It is not impossible it would just require a little extra thought and planning. If your data is already in this format when in your system when it arrives at the SLK2511 than you are already set up to do this.

    The SLK2511 device is simply a serializer, its interface is just not a standard GbE interface like the TLK1221 but it supports the GbE data rate. So, nothing will "happen" if GbE data is present on its interface, the user just needs to be aware of the fact that the data will have to be read in and out of the device in a none typical way. For instance, on the SLK2511 bits 0-3 (4 bit register on its input) may be on TXDATA0 while bits 4-7 will be on TXDATA1 and so on... So the user would simply have to plan for this when writing to and reading to and from the SLK2511. I hope this helps, please let me know if you have any more questions?

    Regards,

    Michael Peffers

    High Speed Interface Applications    

  • 0 in reply to Michael Peffers
    Prodigy 100 points

    Hi Michael

    Thanks for your reply.

    The SLK2511 will be going between an FPGA and a SFP, which should mean that using GbE will be possible, the HDL is being written fresh for this so this shouldn't be a problem. It does sound like we will be able to use GbE if we write the appropriate HDL. 

    Can you give me some more details on how the SLK2511 behaves when receiving Gigabit ethernet data? 

    We will be having the device in auto rate detection mode, so will the CDR still work appropriately? Are there any problems with the reference clock not being related to the GbE clock rate?

    I assume the RATEOUT[1:0] pins will just be in a indeterminate state?

  • 0 in reply to Andrew Cottrell
    TI__Mastermind 20820 points

    Hi Andrew,

    The SLK2511 is a full duplex transceiver. In the transmit direction the device reads in data 4 bits at a time through the 4 bit shift register at its input and serializes the data in a round robin format. The receiver demultiplexes the GbE data and outputs it in 4-bit words with arbitrary boundaries (the byte boundaries would have to be determined by the receiving device). There are no 802.3 PCS functions. The frame synchronization function in the receiver only works for SONET data, so this should be disabled by pulling FRAME_EN low. The CDR will have no issue working with the GbE data rate.

    GbE is very similar to OC-24 (1.244Gbps) so the clock and data frequencies are scaled by 1.25/1.244. So you would configure RSEL0 as 1 and RSEL1 as 0 to achieve OC-24 or a GbE mode. The reference clock rate is set through the REFCLKSEL pin (0=622.08 / 1=155.52) and you would select your desired frequency and simply over clock the device slightly by the 1.25/1.244 ration. This yields you a reference clock of either 625 or 156.25MHz.

    I think the auto-rate detect will be of little use in a GbE application but the RATEOUT pins should resolve to be 10 [0:1]. This feature is meant for SONET applications since there is many variants of SONET while there is only one GbE.

    Regards,

    Michael Peffers

    High Speed Interface Applications

  • 0 in reply to Michael Peffers
    Prodigy 100 points

    Excellent. Thank you.

    This is exactly the information I was looking for. 

    SONET is our primary application for this device, but GbE is a nice little bonus feature if we implement it properly. 

    Cheers,

    Andy