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Valued Contributor III
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cyclone4 ibis models for OCT outputs wrong?

Hi to all. 

I am using quartus prime 16.1.2 to generate the ibis model I / O to do the signal integrity. 

I have a 3v LVTTL output line (fFPGA) that I have to be connected to an external chip. 

In "pin planner" if I disable a series termination is generated a ibis model with 27.9 ohms output driver impedance 

If i put series 25 ohm without calibration is generated a ibis model with with 11.7 ohms output driver impedance. 

If i put series 50 ohm without calibration is generated a ibis model with with 11.7 ohms output driver impedance also. 

where am I wrong? 

I insert the simulations that confirm what I said: 

BEst regards.
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