Hi, I tried to apply the stimuli using modelsim to the sequential adder that I described in vhdl. In particular: - Hi, I tried to apply the stimuli using modelsim to the sequential adder that I described in vhdl. In particular: 1) I tried to generate the clock signal like this (with create wave): here is the screenshot: But doing so it does not work, num1 is the first number to be added num2 is the second number s, the result always fixed to zero rst is the reset active low here is the result of the simulation: 2) I generated the clock like this : Now the result is correct. Why in the first case is it wrong? Thanks a lot . Replies: Re: Hi, I tried to apply the stimuli using modelsim to the sequential adder that I described in vhdl. In particular: Hi, Glad to know that our suggestion helped to resolved your issue. Thanks, Vicky Replies: Re: Hi, I tried to apply the stimuli using modelsim to the sequential adder that I described in vhdl. In particular: Thanks a lot !! I solved, the result is now correct as you can see from the photo with the new version of the software !! We see that the old version had some problems ... thanks again really Replies: Re: Hi, I tried to apply the stimuli using modelsim to the sequential adder that I described in vhdl. In particular: Hi, Thanks for the details. Why don`t you use latest Free Quartus(Lite) & Modelsim starter versions? http://fpgasoftware.intel.com/18.1/?edition=lite&platform=windows&download_manager=dlm3&product=modelsim_ae#tabs-2 I would like to suggest you, try at your end with latest versions also as mentioned vector waveform in previous post. I am looking forward to listen you. Thanks, Vicky Replies: Re: Hi, I tried to apply the stimuli using modelsim to the sequential adder that I described in vhdl. In particular: Hi, Which modelSim edition & version are you using? would you like to provide project files archive? Please check the links below & if possible try at your end & let me know how it works for you. https://www.youtube.com/watch?v=7yKO3PFNiMQ https://www.youtube.com/watch?v=a8JAkKhxlQI Regards, Vicky