[IBIS-Users] 3.3V I/O, 5V tolerant

Hello IBIS experts,

I'm creating a model from HSPICE using S2IBIS2 vers. 2.1 and have a question.

If my buffer is 3.3V i/o, but is 5V tolerant, and am using:

Voltage Ref: 3.3 3.0 3.6
Pulldown Ref: 5.0 4.5 5.5
Pullup Ref: 0 0 0
Power Clamp Ref: 5.0 4.5 5.5
GND Clamp Ref: 0 0 0

I was thinking this should vary my voltages from -5V to 10V for the clamps, but it does not.  It instead varies from -Vcc to 2Vcc as usual. 

Is this how I should be setting this up?  

Thanks,
Gio 

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