command to measure noise margin

[prakash.na@gmail.com]

Hi all,
I want to automate the measurement of vil,vih,vol,voh. I tried to sweep
i/p
'pad' and try to find the value of 'pad' at which derivative of output
'din' is unity.
..meas vil find v(pad) when deriv(v(din)) = 1
But the command is not working.
Also, since there are two such unity slopes, could anyone tell how can
we
differentiate them to get Vil & Vih. I feel for Vol/Voh, we can repeat
the measure statements, by just changing v(pad) to v(din).

Please comment on the above and inform, if anyone knows how to get
vil,vih,vol,voh, by commands in spice.

Regards
Prakash