Digital Simulation Problem, Xspice vs. VHDL

[Tree Haven Technologies]

Hello EWB friends.

I am currently experiencing a problem with a mixed mode/digital simulation.  The main problem is that the component that I am trying to simulate, a differential rs-485/422 interface transceiver, isn't commonly modeled using xspice syntax.  Instead manufacturers and engineers that work with these interface components offer models written in VHDL (I suppose this is because creating this component in xspice is difficult/insufficient).  This transceiver converts a differential analog rs-485/22 input signal to a TTL (0-5v digital) output and vice versa.

I am using Multisim V.10.  The good news is that Multisim v. 10 supports mixed mode simulation using components modeled in VHDL.  The bad news is that NI has discontinued Multi VHDL, which assembles the VHDL model into the .vx file format that is required for simulation with multisim.  This is a problem for me; I understand that Multi VHDL v.8 works fine with Multisim v.10.  Well that’s great and all, but NI does not sell Multi VHDL .8 anymore, it has been discontinued.

After weighing out my options I see two possible solutions to my problem.  One is to obtain a copy of Multi VHDL v.8 some how, or have someone who owns the discontinued software to convert my VHDL model to .vx format for me.  Two would be to design an Xspice sub circuit for this component (possibly a very slow and painful process). 

I have noticed that some digital components are modeled using HDL and/or Xspice syntax; other components are only modeled using HDL (due to complexity).  I have read and reviewed the Xspice user manual and examined its primitives.  From what I understand the component that I am trying to simulate could be created as an xspice sub circuit, although most/all interface components are simulated with HDL.  Does anyone know the limitations of xspice and what digital components are impractical to simulate using xspice? (Besides the obvious like MCU's and FPGA's)  Or could anyone with Multi VHDL v.8 help me out and convert this file to .vx format?

This has been an on going simulation problem for me.  I use analog interface to digital covertering drivers/receivers in the majority of my circuits and cannot simulate them using multisim.  Any input, advice, or help would be greatly appreciated.

Here is the VHDL model that I am trying to assemble to a .vx file / trying to translate into xspice syntax.  I converted it as a .txt so it could be posted, was originally a .vhd.

Thanks,

SPM

[lacy]

I have Mutlisim 10 and under the simulation tab there is VHDL Simulation. Apparently in mine it is only a demo, but you can create VHDL components. I tried compiling your file, but it tells me that it is too large for the demo. It also says this " Better yet, purchase the fully function simulator by calling your local Electronics Workbench reseller".

"For information about how to purchase the Multisim VHDL simulator, visit the Electronics Workbench home page at http://www.electronicsworkbench.com"

The version number says 5.15a. This sounds like it may be old and not what your after. It problably would be best to contact NI or look on their website to see what may be available. It may be that you can purchase this as an add-on for Multisim 10, but I am not certain of that.

Sorry I couldn't help more.

[lacy]

Apparently, what I have is a legacy version demo that has incorporated itself into Multisim 10. I looked in my folders and I do not see anything that says anything about VHDL.  There is something called code modelling available. In mine it is in a folder called "codemodl". I have never used it, but from what I understand you can program your component in C and then compile it with the tools in the folder.

I don't know if this helps at all, but that is all I know.

[Tree Haven Technologies]

Lacy,

Thanks for your help,  I think I will give the code modeling a try.

[Tree Haven Technologies]

Lacy,

Is the code modeling feature only available in the power pro edition of MultiSim?  I am working with the base edition and am having troubles finding the file that you described above.

[lacy]

Unfortunately, I believe that it is. I am sorry. I have to quit assuming that everyone has the Power Pro Version. Have you searched the Internet? There may be some free VHDL programs out there. If not free, you may find a demo that will get you what you need.

I wish I could have been of more help.

[GarretF]

Code modelling is available in all versions of Multisim. The directory lacy was refering is located at C:\Program Files\National Instruments\Circuit Design Suite 10.0\codemodl.

There are some basic instructions in the USER sub-directory (MAKE_DLL.DOC), and much more substantial instructions including an example in section 6.13 of the Multisim User Guide (Start > Programs > National Instruments > Circuit Design Suite 10.0 > Documentation > Multisim User Guide). The guide is written for Visual Studio 6, but I have also used it with Visual Studio 2003 and 2005 by running the appropriate VcVars32.bat.

[GarretF]

Unfortunately, my previous post contained incorrect information. Code modeling is only available in the Power Pro edition, as Lacy correctly indicated.

[lacy]

Garret, Can this individual still purchase a VHDL program from NI even if it may be an older version?

[GarretF]

Unfortunately, MultiVHDL is obsolete software and is no longer available for sale.