Mentor v8.6_4 User Manual
Command Dictionary
Select Iddq Patterns
FastScan and FlexTest Reference Manual, V8.6_4
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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.
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.
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.
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.
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.)
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.
IDDQ measurements can reach the specified test coverage.