Oscilloscope proteus - problem

[DEJANO]

Dear friends:

I am working with Proteus 7.7 and making a simulation with 74HC04 as show in the figure
The frequencia that appear first is 1MHZ.During this pulse train I integrate the signal and shape a pulse with a lenght equal the time of the train.But , in the discharge of the capacitor de problem occur.
How we can see, the format of the signal at points R and E ( red trace and green trace respectivelly), we can see some steps.
I don't understand why this steps.
Does anybory have an idea about?
If I make some mistakes my apologise in advance. My english is not so good.
Thanks everybody

 

[bigdogguru]

Can you upload your simulation? I would like to take a closer look at what you are referring to.

 

[DEJANO]

Hello bigdogguru

Thanks a lot by answer!

I already uploaded the simulation. The attachments (signal_lcd end signal_lcd1) at the botton of my post is oscilloscope and the circuit respectivelly.
I made other circuit using the same 74hc04 and fix this stair steps, but I'd like understand why the simulation of proteus show this wave form

waiting answer.......

 

[bigdogguru]

I only see two JPG thumbnails of the project and oscilloscope, can you upload the actual Proteus project? You'll have to zip it up first.