Ethernet LAN Ethernet PCS question.

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Subject Author Date
Ethernet PCS question. Pranay 06-04-08
Posted by Pranay on June 4, 2008, 5:45 am
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Hi,

I designing an Elastic buffer for Ethernet, I would like to insert/
delete I1 and I2 characters.
I1 = K28.5 & D5.6,
I2 = K28.5 & D16.2

I would like to know if I can delete/insert a part of the I1/I2
character? For example, can I just insert/delete
K28.5 character or should I insert/delete k28.5 and D character as
well?

Normal sequence would be KDKDKDKDKD
After insertion it would be KDKDKKDKDK
After deletion it would be KDKDDKDKDK

is this OK?

My second question is

The 8B/10B encoder would encode the 8B data to either a +ve or a -ve
disparity 10B data.
So is it OK to transmit only I1 or only I2 all the time irrespective
of the current running disparity?
Because the current running disparity would be corrected by the 8B/10B
encoder.


Thanks,
-Pranay.

Posted by Marris on June 7, 2008, 3:29 pm
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If you are intending to transmit the data stream over the physical layer
then you need to maintain the kdkdkd pattern. Normally though elastic
buffers are implemented in the PHY receiver and the symbols are converted to
GMII idle before being sent to the MAC. In this case you can insert or
delete a single byte.

Regarding you second question, I do not have the spec in front of me but it
clearly specifies which idle pattern should be sent. One is used to correct
disparity at the end of frame and the other is then sent continuosly.

> Hi,
>
> I designing an Elastic buffer for Ethernet, I would like to insert/
> delete I1 and I2 characters.
> I1 = K28.5 & D5.6,
> I2 = K28.5 & D16.2
>
> I would like to know if I can delete/insert a part of the I1/I2
> character? For example, can I just insert/delete
> K28.5 character or should I insert/delete k28.5 and D character as
> well?
>
> Normal sequence would be KDKDKDKDKD
> After insertion it would be KDKDKKDKDK
> After deletion it would be KDKDDKDKDK
>
> is this OK?
>
> My second question is
>
> The 8B/10B encoder would encode the 8B data to either a +ve or a -ve
> disparity 10B data.
> So is it OK to transmit only I1 or only I2 all the time irrespective
> of the current running disparity?
> Because the current running disparity would be corrected by the 8B/10B
> encoder.
>
>
> Thanks,
> -Pranay.



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