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FastScan and FlexTest Reference Manual, V8.6_4
2-32
Add Atpg Constraints Command Dictionary
If you change an ATPG constraint for a single internal set of patterns, the tool
continues pattern compression using the new constraints, which can cause the tool
to reject good patterns. Therefore, you should remove all ATPG constraints before
compressing the pattern set.
The Add Atpg Constraints command allows you to change the ATPG constraints
any time during the ATPG process (-Dynamic), affecting only the fault simulation
and test generation that occurs after the constraint changes. The fault simulator
rejects any subsequently simulated patterns that fail to meet the now current
constraints.
Dynamic ATPG constraints do not affect DRC because of their temporary nature.
Static ATPG constraints are unchangeable in ATPG mode, ensuring that DRC
must be repeated if they are changed.
FlexTest Specifics
In addition to the functionality mentioned above, the Add Atpg Constraints
command lets you constrain a net. Thus, if the circuit structure changes and the
ATPG constraints specified on the net pathnames do not change, you do not have
to identify the instance and the pin on which the ATPG constraints have to be
applied. If any ATPG constraint is added to the net, the equivalent pin is found
first and the function is added to that pin instead. Therefore, the Report Atpg
Constraints command may not show the net pathname specified. The constraints
added to the net can be deleted using the same net name.
Arguments
You must choose one of the following three literals to indicate the state value to
which you want the tool to constrain the specified object:
Note
If you constrain a pin by directly creating an ATPG constraint to
the pin_pathname, and then create another constraint that
indirectly creates a different constraint, the tool uses the constraint
that directly specified the pin_pathname (overriding the global
ATPG cell constraint).