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is there an automized way (no WaveformEditor) for generating hws-files out of vcd-format

Digital Patterns for ATE (asic characterization and production) are usually generated script based and therefore fully automized. A common format for digital simulations is the VCD (verilog-change-dump) format which also is the interfcace between the Test-Equipment and the simulation environment. In order to keep a fully automized flow through simulation and testing, it would be nice to be able to do the VCD to HWS conversion automatically by a program.


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unfortunalty there is no other way to import these type of file and convert them to HWS.


sorry that i couldnt help you.


Ramona Lombardo
Applications Engineer, NI Germany
Certified LabVIEW Developer
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I think that what RMatthews was trying to say is that currently, National Instruments does not offer a product that can automatically convert a VCD format file to a HWS file. We do offer the functionality of manually converting the files as part of the Digital Waveform Editor. However, due to the uniqueness of each VCD file, you would have to select things like if a particular signal is the clock signal or if you want to use a set external clock for the signal. That is not to say that creating a HWS file out of a VCD file is impossible. It can be done, but it requires that you write code parse the file, then take the data from the VCD format and save it using the HWS API. If you are interested in taking this route, you will want to look at the IEEE 1364-1995 standard that defines VCD files. This article from Aldec gives a fairly good overview, but you will need to get the standard from IEEE.

Message Edited by Coal Man on 08-19-2008 10:35 AM
Brian Coalson

Software Engineer
National Instruments
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Hi Coal Man,


If you have a list of signal values, e.g.:


S1 S2 S3

0 1 0

X 0 0

1 1 1

0 Z 1



Is it then possible to convert this into HWS format usign some kind of automated tool?


Best regards,


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Yes it is very easy to convert your spreadsheet string into an HWS file if you have LabVIEW. There is a VI built into LabVIEW for converting a Spreadsheet string into a Digital Waveform. Then you can just write that waveform to disk using the Write to File VI from the NI-HWS API.


I included a VI showing how to convert from a String to an HWS file, but I did not have HWS insalled so I didn't add that VI, but it is very simple.



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For converting from a VCD file to a HWS file, there is a tool that has been developed to convert the files just like the DWE can do, but it can be done automatically.  If you are interested in this tool, you can contact NI support by phone, or send me an e-mail directly at  Are you trying to convert a VCD file or a spreadsheet file like you described?
Brian Coalson

Software Engineer
National Instruments
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Hi Jared,




I'm no Labview developer myself, but I will forward your answer to someone who is into that.


The story is, that I'm developing a tool to create test vectors for a device. These vectors should be read by a LabView tool and the device functionality should be verified "in silicon".


Since, the LabView tool requires HWS format a conversion step is necessary. At the moment, we just import the vectors (in spreadsheet format) through the NI tool called "DIgital Waveform Editor", but this is that would preferably be a part of the automated test vector generation flow.


From my perspective, some kind of Unix/Perl script to convert from spreadsheet to HWS format would be perfect, because it would be easily integrated with the remaining flow.


Best regards,


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Hi Brian,


I'm trying to convert from a "spreadsheet" file.


The tool, you are refering to, is that a LabView tool? Please also see my answer to Jared.


Best regards,


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I am interested in this as well. I would like to take a VCD file and generate the digital waveforms with my FPGA card (7813r). It sounds like I would have to create a custom parser, or purchase this Digital Waveform Editor? So the two methods would be:


1. VCD -> Digital waveform editor -> HWS -> PXI-655x card -> Digital out

2. VCD -> custom parser (Labview code) -> custom Labview FPGA code -> PXI-7813 Card -> Digital out


If anyone has ideas or if this has been done before let me know!

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If you wish to use a FPGA card, some custom code will be needed in either case.  Using the Digital Waveform Editor (DWE), you can import the VCD data, but this will only be able to save the data out into HWS, ASCII, or other types of files that are not natively supported by LV FPGA.  So you would need to take the file generated by the DWE, and parse it to get back the data needed by the FPGA code.  This could be fairly simple provided that you are running an OS on your controller, and don't expect the FPGA to have to run without inputs from the controller.


In this case, you can parse the file on your real time or Windows controller, and pass the data to the FPGA card through a FIFO for generation.  The parsing and reading of a HWS or ASCII file produced by the DWE will be easier than creating custom code to read the VCD format, but maybe someone has created a set of VIs to do this already.  I haven't seen them, but maybe they are out there somewhere.


If you have a digital IO card like the 655x, once you convert the VCD to HWS using the DWE, you can just pass the file to the HSDIO driver and it will be able to produce the waveform from the VCD file.  This is probably the easiest and most straightforward method, but if you already have an FPGA card, or need to do some custom FPGA work, then you may want to do the extra work of parsing the file for FPGA.

Brian Coalson

Software Engineer
National Instruments
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