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Speed up the Simulation time


Hi, i'm new to Multisim n m having difficulties simulating 8051 on it.......because i've given delays in my code and the simulation is running very micro or milli seconds....... i need to make the time step equal to the real 1 second...... plz guide me how to do this...... see the attached image for reference.......Best Regards Kazim


in case if its nt possible to achieve the simulation at 1second per step...... advise me a way to make it as close to 1 sec as possible....thanks plz rply....

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Message 1 of 8

Real time simulation with Multisim is not possible. There are too many mathmatical operation occurring within the simulation engine and this, I am sorry to say, is why it not possible to simulate in real time.


The best you can do in most cases is to take TMAX from 1E-005 to 1E-003. This will dramatically increase the simulation speed in some cases. This is dependent on a cetain of factors such as complexity of the circuit and frequency in the circuit.


The time in the lower right corner represents what I call "circuit time". This is the amount of time a real circuit would produce the results. Now it may take minutes of "real time" for the simulator to simulate seconds of "circuit time" depending on your TMAX setting.


There is one other option under the simulation customizations tabs. There is a list of default parameters there that you can change that may also help. The 2 that come to mind are changing the simulation engines Method from Trapezoidal to Gear or vice versa. The other is call RELTOL. This stand fior relative tolerance. It is set now to ..001 your tray dropping this down as low a .1 to see what the effect would be as far as speed is concerned.


This is about the limit of control you can exert to speed up Multisim. If you try to go too far with TMAX or thje other settings then you start running the risk of the simulator returning "Timestep Too Small" errors and not simulating the circuit or your results will not be correct due to the fact that as the simulation speed increases the results are not as accurate.


I hope this helps some as this is about all you can do.  It takes some getting used to, but patience with Multisim is of the upmost. I have gotten use to the slow simulations speeds and I now  I just wait for a while to get my results.

Message Edited by lacy on 11-16-2008 08:59 AM
Message Edited by lacy on 11-16-2008 09:00 AM
Kittmaster's Component Database

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Message 2 of 8
well thats pretty weird.........and pretty unexpected bcz there are softwares out there which simulate in real time and the simulation speed is nt really effected by the frequencies proteus......but may be its not too complex which makes it run faster...........anyway........thanks for replying.....its so kind of you........
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You say there are simulators that can simulate in real time, but do they simulate the ciruit and then present you with a graph of the results? Also do do they have interactive simulation components that you can visibly see working like the LED's?


The reason I am asking is because I had a simular program called SwitcherCad III that done what I am describing above. It did not have a time domain simulation capability. It just graphed the results. It had no interactive instruments like Multisim. You placed a probe on a wire and then it just graphed that particular current or voltage.


Multisim is capable of doing the same and it is 100% faster, but you lose the interactive capabilities like watching LED switch on and off. and it bypasses the intruments like the voltmeter. You can find these under the Analysis options. If you would prefer that meithod over time domain simulation then you could give them a try.


Just trying to explore all options here. You can select whatever method you prefer.

Kittmaster's Component Database

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Message 4 of 8

well i'm not sure that i understood what u meant by interavctive i just want you to look at the video i attached (sorry for the bad quality) shows the LEDs glowing..... bt i'm nt sure if u r talking abt the same thing...........



anyway..... dude i need to simulate an 8051 project on any software which has a multiplier component in multisim everything is available bt its slow as i've a keypad and an LCD in my project...... in Proteus everything is fine bt the problem is that the mixer component gives an has no model plz suggest me a sftware that has 8051 and mixer working in it........i'm so obliged

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* OK I just have read your post but couldn't understand that (interactive) components , did you mean the simulation gives the results simultaneously?

** And how to solve this problem I think you said that the other programs gives the final result or it may not be able to show transient, for example I'm right ??


*** For example I tested a stair light circuit, and the capacitor charges in a long time , of course it's not real time, but to wait for its time is not easy time is slipping away?

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I'm a multisum user. Can u please send me the circuit diagram of digital stopwatch with the use of multisim software along with the working rule.Please help me as soon as possible. Thank u.
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Message 7 of 8



This thread is from almost 4 years ago, so I am not sure if the users involved are still around. In order to get a better visibility for your post, I would suggest you to actually create a new one here.



Camilo V.
National Instruments
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