I am using using cadence 5.1 and AMS embedded to in it. I saw that we have a connection rule which interpreted the analog to digital waveform but it only realize 1.8v.
How can I change it to make it work with correct voltage level for 3.3v ? currently all will be just logic "1' .
That's a very old and unsupported version (IC5.1 came out in 2004, so over 15 years ago, and the last hotfix was in 2011). The connect rules can be set up in ADE using Setup->Connect Rules, and you could just pick the 3V rules (connectLib.ConnRules_3V_full_fast) from the built-in rules. Or you could hit the customise button next to that and change the supply level to 3.3 if you want it to be more precise.