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RGMii Signal Spacing 1000b 125Mhz

Question asked by DAVID SABALESKY on Jun 12, 2019
Latest reply on Jun 14, 2019 by igorpadykov

It is accepted that cross talk is generally reduced when S >3W or S>5W for aggressive lines as a rule of thumb.

Are general constraints in regard to  RX/TX Data[3..0] trace spacing applicable to RGMii when at 125MHz?

 

Due to the reduction in the magnitude of induced reflections on the near-end and far-end with each round trip cycle, at light speed,  in conjunction with the clock edge being skewed 1.5ns-2.0ns, is the effective cross-talk at the clocked edges greatly reduced? -- given that multiple cycles will occur relative to track lengths.

 

If this is true then the spacing between the Group Data lines, Rx or Tx, can be reduced. This is especially useful for high dense designs allowing for tighter group spacing and eases constraints during critical signal routing. Given the track lengths and known skew, I believe it is possible to determine that their is an actual minimum S to maintain SI, signal integrity. Spacing between different groups still needs to be maintained for SI, signal integrity.

Are there any SI tools that does this calculation?

 

All feedback is welcome.

If there are any SI experts that can respond to this it is greatly appreciated.

 

Thanks,
David

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