There are a few methods for creating and editing digital test patterns. The first is to create a model of the entire system and to let the model generate test vectors automatically. While the actual generation of test vectors is convenient, it's not always feasible, either economically or in terms of time, to create such a model. Another test vector generation method is to produce the test patterns algorithmically in the application development environment or to manually enter digital states directly into a spreadsheet tool such as Excel. While convenient for simple vector sets, these methods quickly become cumbersome as test pattern sets grow. Ideally, a designer would have a software tool that can speed their design characterization by linking to existing test vectors and providing a powerful, intuitive interface for editing test vectors.
For digital characterization, the National Instruments Digital Waveform Editor provides a convenient interface for creating and editing digital patterns for both small and large test sets.
If a designer has existing test patterns from spreadsheet or math packages, they can import them in ASCII format. Or if your design is done in a VHDL simulation package, designers can import the simulation into the Digital Waveform Editor through the Value Change Dump (.VCD) format.
The Digital Waveform Editor also includes several built-in fill patterns to help designers easily create new patterns or add additional signals to their existing test patterns. These fill patterns include pseudorandom bit sequence (PRBS,) count up/down, marching values, toggle or dc value. Regardless of whether designers start a new waveform or import an existing waveform, they also view the waveforms graphically and edit them for new devices or new test conditions. They do that by toggling individual bits, setting bus values and modifying entire selections of data with the rotate, shift, and invert data features. When they are ready to test the waveforms with hardware, they can import them into their Application Development Environment, such as LabVIEW, LabWindows/CVI or C. The NI Digital Waveform Editor can help speed digital design characterization by providing an intuitive, interactive tool for creating and editing digital test patterns.