Stratix IV differential LVPECL Ibis model

Hi

i wanted to simulate a differential LVPECL output using ibis models. The models i've found only include LVPECL inputs, but the stratix 4 handbook says, that there are LVPECL outputs too:

--- Quote Start ---

In Stratix IV devices, the LVPECL I/O standard is supported on input clock pins on

column and row I/O banks. LVPECL output operation is not supported in Stratix IV

devices.

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So what model do I have to use?

Thanks for your help.

Thomas