Though I appreciate your attempt I must say your circuit won't work.
When connecting a pull-up and a diode the way you suggest it will only cause the diode to let through a 1 from the 40106 and it will prevent a 0 from pulling down the input (P3.1) so this pin will always be high.
It would be better to put a series resistor between the 40106 and P3.1, but I agree with Steve, I suspect a different power supply from the 40106.
For connecting a UC to the outside world I mostly use a ULN2803 or 2804.
These devices have open collector outputs and do not generate any voltage except the one from the pull-up.