Ethernet PCS question.

Jun 04, 2008 1 Replies
P

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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M

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.

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