Command Dictionary | Select Iddq Patterns |
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statement. (FastScan gives the normal fault simulation message after each set of 32 patterns.) The tool uses this simulation to calculate the final test coverage and also to give credit for the possibly-detected faults.
After the tool finishes this IDDQ pattern selection process, you can save the selected patterns to an external file with the Save Patterns command.
FlexTest Specifics
FlexTest may run out of memory during step 1 of the selection process if you are working with a large design with the default -Exhaustive switch active. This is because the -Exhaustive switch causes FlexTest to simulate all the IDDQ measurements, without fault dropping, before beginning the selection process. To do this, FlexTest creates a table to keep track of which faults it detects in each measurement. In some cases the table size can be too large for the amount of available memory.
To circumvent the memory problem, you can use the -Window switch in combination with the -Exhaustive switch to define how many measurements FlexTest is to allow in the table. If you allow fewer IDDQ measurements in the table than the total number of IDDQ measurements in the simulation, FlexTest makes multiple passes until it simulates all measurements.
When you specify the -Window switch, FlexTest still keeps track of the simulation results and enters them into the table. However, when the table is full, FlexTest pauses the simulation and begins the selection process outlined in step 2a. When the selection process is complete on that window’s worth of measurements, FlexTest keeps only the qualified IDDQ measurements in the table. FlexTest then begins simulating the next set of measures, using the remaining space in the detection table. It repeats this simulation, followed by the selection process, until it simulates the entire pattern set. For this method to work, the window size must be at least two times the -Max_measures number (unless the window size is large enough to hold all the IDDQ measurements.)
The -TEst_coverage switch allows you to stop the selection process if the selected IDDQ measurements can reach the specified test coverage.
