ScanWorks^® JTAG Interconnect Development Station Bundle

Model-Based Interconnect Tests

To quickly generate safe board tests with high fault coverage three types of data are needed:

• An accurate description of the boundary-scan features of the board
• An accurate description of the connections between devices on the board
• Information about the IO characteristics of all devices on the board that interact with any boundary-scan devices

The first two types of data were discussed above. The third type is derived from models of non-boundary-scan devices. Although ScanWorks does not need models of the non-boundary-scan devices to generate a test, tests are generated faster and with less manual intervention when ScanWorks has more information.

ScanWorks interconnect test generation will not attempt to drive any net (node) for which it does not have enough information to determine whether another device is simultaneously driving the net (signal contention). Since many boundary-scan nets are also connected to non-boundary-scan devices, information about non-boundary-scan devices is needed to automatically create safe tests with high fault coverage. This information can be added manually through constraints.

Cluster models contain information on non-boundary-scan devices. Cluster models can describe the IO characteristics and some basic logic functions of devices. With the logical descriptions contained in cluster models, ScanWorks can determine whether test signals can be sent through a non-boundary-scan device from an adjacent boundary-scan driver to a boundary-scan receiver. This feature can dramatically increase test coverage. For a detailed description of how models are used to reduce test generation time while safely increasing test coverage, see the whitepaper Sophisticated device modeling is key to optimizing automatic test generation.

Models can be automatically included into ScanWorks tests if strict naming conventions are followed during the design capture process or they can be added manually. Thousands of non-boundary-scan device models are stored in ASSET’s web-based model library, which is available to maintenance customers. Models can also be easily created or modified.

ScanWorks also provides many other useful features. For example, a visual user interface can be used to easily create test constraints that would prevent toggling of specific nets or pins. And to minimize ground bounce, parameters can be set to limit the number of pins or nets that toggle during any scan. Test coverage reports clearly identify the coverage available at the net and pin level. Nets are classified according to coverage and reported as a percentage of coverage in each class. An interactive debugger gives you a view of the vector as it is applied.

Net-level diagnostics are included in the Interconnect Development Station along with the Interconnect Pin-Level Diagnostics. To rapidly isolate defects, the Graphical Fault Highlighting option links a pin or a net from a fault report to a graphical view of the board layout.

Previous : Next                   Page 5 of 8          Back to Page 1