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Generating Test Patterns
Setting Up the Fault Information for ATPG
Note
The Report Statistics command always reports both uncollapsed and collapsed statistics.
Therefore, the Set Fault Mode command is useful only for the Report Faults and Write
Faults commands.
Setting the Hypertrophic Limit (FlexTest Only)
To improve fault simulation performance, you can reduce or eliminate hypertrophic faults with
little consequence to the accuracy of the fault coverage. In fault simulation, hypertrophic faults
require additional memory and processor time. These type of faults do not occur often, but do
significantly affect fault simulation performance. To set the hypertrophic limit, enter the Set
Hypertrophic Limit command as follows:
SET HYpertrophic Limit Off | Default | To percentage
You can specify a percentage between 1 and 100, which means that when a fault begins to cause
more than that percent of the state elements to deviate from the good machine status, the
simulator will drop that fault from simulation. The default is a 30% difference (between good
and faulty machine status) to classify a fault as hypertrophic. To improve performance, you can
reduce the percentage number.
Setting DS Fault Handling (FlexTest Only)
To facilitate fault diagnosis, you can set FlexTest to carry out fault simulation without dropping
faults. The Set Fault Dropping command enables or disables the dropping of DS faults when
FlexTest is in Fault mode. To set DS fault handling, enter the Set Fault Dropping command as
follows:
SET FAult Dropping ON | {OFf [-Dictionary filename] [-Oscillation] [-Hypertrophic]}
When carrying out fault simulation, setting fault dropping “on”, sets FlexTest to drop DS faults;
this is the default behavior of the tool. For detailed information on the options for this
command, refer to the Set Fault Dropping command in the ATPG Tools Reference Manual.
Setting the Possible-Detect Credit
Before reporting test coverage, fault coverage, and ATPG effectiveness, you should specify the
credit you want given to possible-detected faults. To set the credit to be given to possibledetected faults, use the Set Possible Credit command. This command’s usage is as follows:
SET POssible Credit percentage
The selected credit may be any positive integer less than or equal to 100, the default being 50%.
Scan and ATPG Process Guide, V8.2004_2
April 2004
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