I am having severe problems using the logic simulation in Multisim 13 of a pure logic circuit. The circuit has to convert a 4 bit binary code into a decimal number made visible on 2 hexadecmial display units. I am using a subcircuit to make it better readable. The wordgenerator is programmed to make 12H steps, starting with input 0EH en running to 0H on the lowest 4 binary lines. It has to ron at 200 Hz, so after the burst is done all 16 binary input combinations will have passed by. It all runs beautiful, see the added pictures.
What is wrong?
The 4 Lamps X1..X4 attached to the 4 binary signals show the logical values of the binary word generator outputs. Also a separate hexadecimal display U1 is used to show the hex-value. That works fine too, they both agree and give the same values. On the input terminals of the subcircuit SC1 is of course the same set of binary values on the Logic Analyzer this can be verified. Also, the outputs of subcircuit SC1 gave the right values voor "15" on a hexdisplay. you can check this in the Logic Analyser's timing diagram: all is fine. The same outputs of SC1 are also brought to a set of two 7-segment HEX displays
But there it goes wrong! Both 7 segment Hex displays together show "00" which should be "15" as can be seen in the Logic Analyser output!
And when I use Step in the Wordgenerator, it happens also now and then that this discripancy happens. I find this very annoying and hard to explain to my students.
What is wrong with this logic simulation in Multisim 13.1 ????
I was able to reproduce your situation.
I use MS14
the key is to pay attantion on freq setting of world gen-r -
if it is low as 50 Hz - it works fine in all modes.
but when it is high, like 200hz or even higher like 2000 , it begins to bumble - and as higher freq as more mistakes.
I guess there is problem with calculations and posible work out is to use low freqs for simulation/
sorry, no images, I do have screen captures, but these files are too big
with hope it helps
Hi Michael, reading your reply about not having a screen capture tool, I have good news for you. If your running windows, then you do have a built in capture tool and a nice one at that. It is something included with Windows, but one of those things you have to stumble across which I did one day, and now I capture screen images with ease
The tool name is snippingTool.exe and you can envoke it from your run window, or make a shortcut as I did. I just thought I would mention it based on what you said earlier, and I hope it helps you out.
See image below.
hello , thanks for the info.
I guess I did not explained my self properly.
the matter of fact I do use screen capture tool (Snagit32) and I have made a few videos for that post., but, they are too big and that forum does not accept mp4 file extension.
I just tried that Snipsnip tool - it works fine for sreenshots, but does not do videos.
thanks for replay anyway -
I tried 20 Hz .. 50 Hz and yes you're right, there is a sensitivity for above around 30 Hz, then the errors became worse. At 20 Hz it almost runs flawless.
But even knowing this, I still consider this as a bug in Microsim: it should be not that sensitive to this setting.
Thanks anyway for you response.
I will post also the lab2 circuit later on, once I have tested it more thouroughly.
Hello, thanks for response
so if it solved your problem - check that post as solved/
with hope it helps