Test Connections
Geotest’s DIOEasy waveform editor and display software offers test engineers a full-featured software tool set for creating, editing and importing digital vectors for use with Geotest’s digital I/O products. Geotest has recently added an option, DIOEasy-FIT, which supports the importing and conversion of WGL (waveform generation language) files for use with Geotest’s GX5290, GX5280 and GX5055 digital instruments.

WGL overview
WGL is a data description language supported by Test Systems Strategies, Inc. A WGL file uses an ASCII representation of the digital waveform data, so it can be edited using any text editor. WGL is also an intermediate file format used by the semiconductor industry for converting digital test patterns from a logic simulator to tester hardware, and back again.

Test information is represented in a WGL file using a structured, free-form language with small, specialized structural blocks contained within larger, more generalized blocks. A full discussion of the WGL language and syntax is beyond the scope of this article, but can be found in the TDS Languages Guide, Version 2007.1, published by Test Systems Strategies, Inc. The benefit of WGL is that any digital instrument or tester that can read or write test patterns using the WGL language, has a link to any simulation tool that also supports WGL, either directly between the simulator and tester hardware, or indirectly through other translators or filters.

A detailed discussion about the WGL file format can be found here.

WGL can represent simple stimulus/record digital test patterns, as well as more complex stimulus/response patterns that incorporate realtime compare functionality. Because several Geotest DIO products support both functions, this article discusses importing WGL files both ways.

Activating DIOEasy-FIT — WGL Import Toolkit
The Geotest WGL import utility is a licensed product of Geotest, Inc. Once purchased, the File Import Translator (FIT) license can be activated by entering a unique license string for the system. The license string is based on the computer ID of the host system where the license will be installed, and can be found from DIOEasy by clicking Help\About DIOEasy\Setup License, and selecting Setup License (see Figure 1).

Click here to link to our product page.

File Import Translator License Setup
Figure 1 — File Import Translator License Setup

The computer ID is the 10-digit code displayed at the bottom of the DIOEasy License Setup dialog — XXXX YYYY ZZ in Figure 2. To obtain the FIT license, open a Magic incident, request an FIT license, and provide the sales order number of your FIT purchase and the computer ID. You will receive a license that is unique to the system whose ID you provided. Enter the license string in the License String/File text box and click OK.

Computer ID Code
Figure 2 — Computer ID Code

The Geotest WGL import utility is supported by DIOEasy, Geotest's interactive digital development tool set, and via the GtDio32.dll API, a Dynamic Link Library of DIO software functions. The full list of these DIO functions and their syntax and uses can be found in the DioSoftwareProgRef.PDF document. This document is included with the GtDio.Exe driver installation package, which is available at the Geotest Web page:

The DioFileImportWgl() Function
One of the functions included in the GtDio32.Dll is DioFileImportWgl(). This function is an import utility for reading WGL formatted digital test patterns and converting them into a Geotest DIO formatted file. The file can be loaded to the instrument, opened for viewing and editing using DIOEasy, or opened under program control so digital pattern data can be accessed from within a test program. The syntax for this function and an example of its usage are provided below.

DioFileImportWgl (pszSourceWglFile, pszDestDioFile, nConversionMode, nBoardType, pdMaxFrequncy, pdwMaxSteps, pszError, nErrMaxLen, pnStatus)

pszSourceWglFilePCSTRSource file
pszDestDioFilePCSTRTarget DIO file name
nConversionModeSHORTConversion mode:
   0 DIO_FILE_WGL_TO_DIO: Standard DIO file
   1 DIO_FILE_WGL_TO_DIO_RTC: Real-Time Compare DIO file
nBoardTypeSHORTSets the target supported DIO board type:
   0x55 DIO_BOARD_TYPE_GX5055 – Gx5055 DIO board type
   0x70 DIO_BOARD_TYPE_GX5290 - Gx5290 DIO board type
   0x75 DIO_BOARD_TYPE_GX5290E - Gc5290 Express DIO board type
   0x7A DIO_BOARD_TYPE_GX5295 - Gc5295 board type
pdMaxFrequncyPDOUBLE 0 for the WGL importer to use the best vector clock frequency, otherwise overwrites the vector max frequency
pdwMaxStepsPDWORDThe maximum number of steps to convert
pszErrorPSTRBuffer to contain the returned error string
nErrMaxLenSHORTSize of the buffer to contain the error string
pnStatusPSHORTReturned status: 0 on success, negative number on failure

Importing WGL in DIOEasy
To import a WGL file into a DIOEasy digital file, click File from the menu bar and select Import WGL File. A dialog will pop up prompting you to select the source WGL file and the destination DIO file (Figure 3). In addition to specifying the source and destination files, you must also select the target DIO instrument from the drop-down list (see the nBoardType parameter above), and specify whether to use the default values for the test frequency (data rate) and file size. When importing a WGL file, the import filter will determine the optimal timing to use based on the capabilities of the DIO instrument selected and will set the clock rate accordingly.

DIOEasy WGL Import Dialog
Figure 3 — DIOEasy WGL Import Dialog

One final selection is whether to translate the WGL patterns for stimulus/record operations with Post Process compare, or to translate the WGL patterns for Real-Time compare. Real-Time compare has the advantage of performing a hardware comparison of the UUT response against a pre-loaded expected response.

Because the compare process is done in hardware and at the speed of the digital engine, pass/fail results are instantaneous. However, Post Process compare requires software to read the recorded information from the DIO hardware, and compare each step against a reference file that contains the expected UUT response. The WGL import filter supports both test methodologies, as do selected Geotest digital instruments.

Once the import process completes, a new DIO file is created and automatically loaded to DIOEasy. The file can be viewed and edited, the same as any other DIO file, and the test file can be loaded to the DIO hardware for execution.

Timing translation
A common concern when porting digital tests from the simulation environment to hardware is how timing parameters are interpreted. A simulator can generate waveforms and tests with picosecond timing resolution. This is far beyond the capability of the actual hardware test system. The WGL import filter will try to fit the timing parameters into the capabilities of the hardware by adjusting the clock frequency to accommodate the minimum phase resolution between the signals. This is done by dividing the WGL test cycle time by the minimum phase difference between the various signals.

For example, if a WGL file has a cycle time of 1uS (1 MHz data rate), but there was a setup parameter of 10nS between a clock and data channel, the importer would calculate a new data rate for the hardware that meets both criteria. In this example, the digital hardware would run at 100 MHz, providing the 10nS phase resolution. This translates to more digital test vectors loaded into the hardware than the native WGL file represents. In this case, 1uS period / 10nS resolution results in 10:1 pattern depth on the digital tester. So if the WGL pattern file was initially 1M vectors, the pattern file loaded to the hardware would be 10M vectors.

In some cases, the simulated phase resolution exceeds the capability of the tester, so the WGL importer maintains a proportional relationship between the signals. For example, assume the cycle time is 50nS and some of the channels in that cycle change on 5nS phases (200 MHz resolution). The WGL importer determines that one WGL cycle will require 10 DIO cycles (50nS period / 5nS resolution). Assuming the hardware is the GX5292, the minimum cycle timing for this instrument is 10nS (100 MHz maximum frequency), so the pattern data rate would be set to 100 MHz, but you would maintain the 10:1 pattern ratio to keep the phase relationships proportional to the original WGL pattern (50nS period / 5nS resolution) = (100nS period / 10nS resolution).

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