HI

Ibis model provides the analog characteristics of digital circuits that helps the users to simulate the design. IBIS modelling basically came into existence to protect the IP rights of a semiconductor vendor.

The IBIS model of a design only provides the characteristics of the device and hence it hides the internal design.

all the above characteristics are generic to a digital design the gnd and power clamp model provides the V/I characteristics of the gnd and power clamp diodes that might be present in the circuit.

the pullup and pull down curves provide the V/I characteristics of the pull up and the pull down transistors in the output pin( it depends whether ur output pin is a push/pull, open drain, open ECL or open sink type)

the rising and the falling waveforms provide the switching V/t characteristics of the output pin...

so u must understand about the device functionality before creating an IBIS model to develop a better model.....

more info can be found here :

http://www.eigroup.org/ibis/

SESHADRI