What is the methology of sending signals via Bi-Direcional MOSFET?
An output will act the same as a switch to ground, as you have drawn it, rather than a switch to 3.3V (in reverse, of course). 

When the output is low it will conduct to ground like the close switch. It won't do much when it is high. Your switch has to mimic the output. If you want to get closer to the real situation, you can do this: 







simulate this circuit &ndash; Schematic created using CircuitLab

There are actually two MOSFETs in a CMOS output, one of which acts as the N.C. contact and the other as the N.O. in the above mechanical switch.