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Design >> High-Speed I/O Design >> Looking for study report on 128b/130b coding
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Message started by neoflash on Jul 29^th, 2010, 5:45pm

Title: Looking for study report on 128b/130b coding
Post by neoflash on Jul 29^th, 2010, 5:45pm

Hi,

PCI-E is adopting 128/130 coding to replace 8b/10b encoding.

I'm looking for materials studying the code performance, such as transition density, DC balancing, maximum run length...

Thanks for the sharing of the information.
Neo

Title: Re: Looking for study report on 128b/130b coding
Post by casual on Jul 30^th, 2010, 12:40am

I think the similar theories of 8B10B may be applied to 128B/130B to achieve dc balance. The 2 preamble bits is used as sync payload.
But the max run length / data density depends on data scrambler.

That means the CDR will be more challenging! It has more DC wander, thus it needs larger CDR bandwidth (around 5-10MHz).
On the other hand to reduce jitter (clk), Tx/Rx PLL bandwidth must be reduced.