ATPG Basic Tool Flow
The below figure shows the basic process flow for the ATPG tool.
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| ATPG Basic Tool Flow |
1. Invoke Tessent Shell using the “tessent -shell” command. Set the context to “patterns -scan” using the set_context command, which allows you to access ATPG functionality.
2. The ATPG tool requires a gate-level design netlist and a DFT library.
3. After reading the library and netlist, the tool goes into setup mode.
4. After performing all the desired setup you can exit setup mode which triggers a number of operations. If this is the first attempt to exit setup mode, the tool creates a flattened design model.
5. After design flattening, the ATPG tool performs extensive analysis on the design to learn behavior that may be useful for intelligent decision making in later processes, such as fault simulation and ATPG.
6. In next step tool begins design rules checking(DRC).
7. After the design passes rules checking, the tool enters analysis mode, where you can perform simulation on a pattern set for the design.
8. At this step you may want to create patterns. You can also perform some additional setup steps, such as adding the fault list.You can then run ATPG on the fault list. During the ATPG run, the tool also performs fault simulation to verify that the generated patterns detect the targeted faults.
9. After generating a test set with the ATPG tool, you should apply timing information to the patterns and verify the design and patterns before handing them off to the vendor.
ATPG Tool Inputs and Outputs
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| ATPG Tool Inputs and Outputs |
The ATPG tool uses multiple inputs to produce test patterns, a fault list, and ATPG information files.
ATPG Process
The objective of ATPG is to create a set of patterns that achieves a given test coverage, where test coverage is the total percentage of testable faults the pattern set actually detects.
ATPG consists of two main steps:
1) generating patterns
2) performing fault simulation to determine which faults the patterns detect.
Mentor Graphics ATPG tools automate these two steps into a single operation or ATPG process.
The two most typical methods for pattern generation are random pattern test generation and deterministic pattern test generation.
Random Pattern Test Generation
The ATPG tool uses random pattern test generation when it produces a number of random
patterns and identifies only those patterns that detect faults.
Deterministic Pattern Test Generation
The ATPG tool uses deterministic test pattern generation when it creates a test pattern intended to detect a given fault. The procedure is to pick a fault from the fault list, create a pattern to detect the fault, fault simulate the pattern, and check to make sure the pattern detects the fault.
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