In SX Microcontrollers, SX/B Compiler and SX-Key Tool, George Herzog wrote:

Guenther really put a lot of effort and thought into the original thread about EMI.  I was pretty much the 'student' and he the 'teacher' on that one.  Anyone that doesn't understand his shorter reply herein, should look it up.

Guenther stated that most, if not all the problem, originates on the EMI in the power lines.  Apparently reflections from the oscillator and the reflections from switching  logic at regular periods of time cause the problem.  [I suppose that different software might exhibit different resonant peaks.]

Regarding Paul Baker's question -- I would guess the reason for 4 ply being more effective must always come down to creating a tuned circuit via a large power filter capacitor which implies an impedance effect and a resonant effect.  The capacitance just knocks the tops off the high frequency resonance.

Additionally, there is might be 'a halving' of EMI created by the internal floods create a 'semi-shield' for the individual leads. The Vss and Vdd EMI are 180 degrees out of phase, so not much goes beyond them if the surfaces are nearly equal and nearby.  This would be partially similar to eliminating cross talk in ribbon cable by having alternating wires grounded.

I guess we have an entirely new electronic concept - 'the development Autonomy of the digital information from the power source that it depends on.'  That is one that the chip manufactures ponder as a speed barrier.

And, I have been as 'guilty' as William of doing everything I can to make a susceptible EMI board.  In the beginning, you just think that the routing software can 'intelligently' layout a board, but there is  really an art to a genuine production run, stable product.

I suspect it is nearly all dampening, not amplfying.

It would be wonderful if the manufacturer could include a set of small by-pass capacitors within the silicon or at least the package as a 'first line of defence.  It would make a more marketable product as it wouldn't be so tricky to product a board.

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