Orcad simulation problem

[DimaA]

Hi, i'm trying to simulate a PRBs generator using shift-register and I have few problems:
First, why voltage on the resistor is constant and doesn't fall down because of capacitor?
Second, what is the strange output of the circuit (the red lines).
Thanx.

 

[papyaki]

Hi,

First, set IC parameter of the 10uF capacitor to 0V.

Then use two schmitt trigger inverters in series between 330ohms/10uF node and MODE input of 7495.

Remember that the time constant of the RC is 3.3ms, so simulation period would be long regarding to clock period (100ns).

The red lines indicate that the state of the outputs is unknown