Isometric control data generation for test compression

1. A method, executed by at least one processor of a computer, comprising:

generating a test cube for each of a plurality of faults to obtain a plurality of test cubes;

determining operational mode information and a hold-toggle pattern based on the plurality of test cubes, predetermined size and toggle rate for the hold-toggle pattern, and a predetermined maximum number of device inputs for full-toggle scan chains (scan chains operating in a full-toggle mode), wherein the operational mode information determines which scan chains in the scan chains to be the full-toggle scan chains and which scan chains in the scan chains to be hold-toggle scan chains (scan chains operating in a hold-toggle mode) during a shift period, wherein the hold-toggle pattern determines in which shift clock cycles in a segment of consecutive shift clock cycles the hold-toggle scan chains receive bits based on corresponding bits of a test pattern during the shift period, wherein the hold-toggle pattern repeats multiple times during the shift period, the shift period being a period when the test pattern is being shifted into scan chains, and wherein the device inputs are inputs of a device coupled to the scan chains and configured to allow a small number of input lines to feed a large number of the scan chains; and

generating test patterns based on the operational mode information and the hold-toggle pattern.

2. The method recited in claim 1 , further comprising:

performing fault simulations to determine, based on whether there are still faults left in originally targeted faults not detectable by the test patterns, whether to repeat the generating test cubes, the determining operational mode information and a hold-toggle pattern, and the generating test patterns.

3. The method recited in claim 1 , wherein the determining operational mode information and a hold-toggle pattern comprises:

determining the full-toggle scan chains based on toggle ranges for each of the plurality of test cubes; and

determining the hold-toggle pattern using a relaxation algorithm and based on the full-toggle scan chains, the plurality of test cubes, and the predetermined size and toggle rate for the hold-toggle pattern.

4. The method recited in claim 3 , wherein the determining the full-toggle scan chains comprises:

determining the toggle ranges for each of the scan chains for the each of the test cubes;

determining chain-reduced toggle ranges by combining the toggle ranges for each of the scan chains for the each of the test cubes based on the predetermined size for the hold-toggle pattern;

determining reduced toggle ranges for the each of the test cubes by combining the chain-reduced toggle ranges based on the predetermined toggle rate for the hold-toggle pattern; and

determining the full-toggle scan chains based on scan chains of which the chain-reduced toggle ranges cannot be combined into the reduced toggle ranges due to the predetermined toggle rate for the hold-toggle pattern and the number of device inputs available for full-toggle scan chains.

5. The method recited in claim 1 , wherein the determining operational mode information and a hold-toggle pattern comprises:

determining the hold-toggle pattern using a relaxation algorithm and based on the plurality of test cubes and the predetermined size and toggle rate for the hold-toggle pattern.

6. The method recited in claim 5 , wherein the determining the hold-toggle pattern comprises:

replacing test cubes having conflicts with a selected intermediate hold-toggle pattern generated by the relaxation algorithm with test cubes generated based on the selected intermediate hold-toggle pattern.

7. The method recited in claim 5 , wherein the determining operational mode information and a hold-toggle pattern further comprises:

determining the full-toggle scan chains based on test cubes having conflicts with an intermediate hold-toggle pattern selected by the relaxation algorithm and the number of device inputs available for full-toggle scan chains.

8. The method recited in claim 7 , wherein the determining the full-toggle scan chains comprises:

ranking scan chains based on the test cubes having conflicts with the selected intermediate hold-toggle pattern; and

using the ranked scan chains and the number of device inputs available for full-toggle scan chains to determine the full-toggle scan chains.

9. The method recited in claim 5 , wherein the determining the hold-toggle pattern comprises:

selecting an intermediate hold-toggle pattern from intermediate hold-toggle patterns generated by the relaxation algorithm based on a specified bits-related cost function.

10. The method recited in claim 1 , wherein the device is an expander in a decompressor.

11. The method recited in claim 1 , wherein the generating test patterns comprises generating compressed test patterns.

12. The method recited in claim 11 , wherein the compressed test patterns are test patterns encoded for EDT (embedded deterministic test)-based decompressors.

13. The method recited in claim 1 , wherein the predetermined size for the hold-toggle pattern is 40 bits or fewer, the predetermined toggle rate for the hold-toggle pattern is two times the scan chain shift toggle rate limit, and the predetermined maximum number of device inputs for the full-toggle scan chains is 2.

14. The method recited in claim 1 , wherein the plurality of faults are a subset of originally targeted faults.

15. One or more non-transitory computer-readable media storing computer-executable instructions for causing one or more processors to perform a method, the method comprising:

generating a test cube for each of a plurality of faults to obtain a plurality of test cubes;

determining operational mode information and a hold-toggle pattern based on the plurality of test cubes, predetermined size and toggle rate for the hold-toggle pattern, and a predetermined maximum number of device inputs for full-toggle scan chains (scan chains operating in a full-toggle mode), wherein the operational mode information determines which scan chains in the scan chains to be the full-toggle scan chains and which scan chains in the scan chains to be hold-toggle scan chains (scan chains operating in a hold-toggle mode) during a shift period, wherein the hold-toggle pattern determines in which shift clock cycles in a segment of consecutive shift clock cycles the hold-toggle scan chains receive bits based on corresponding bits of a test pattern during the shift period, wherein the hold-toggle pattern repeats multiple times during the shift period, the shift period being a period when the test pattern is being shifted into scan chains, and wherein the device inputs are inputs of a device coupled to the scan chains and configured to allow a small number of input lines to feed a large number of the scan chains; and

generating test patterns based on the operational mode information and the hold-toggle pattern.

16. The one or more non-transitory computer-readable media recited in claim 15 , wherein the method further comprises:

performing fault simulations to determine, based on whether there are still faults left in originally targeted faults not detectable by the test patterns, whether to repeat the generating test cubes, the determining operational mode information and a hold-toggle pattern, and the generating test patterns.

17. The one or more non-transitory computer-readable media recited in claim 15 , wherein the determining operational mode information and a hold-toggle pattern comprises:

determining the full-toggle scan chains based on toggle ranges for each of the plurality of test cubes; and

determining the hold-toggle pattern using a relaxation algorithm and based on the full-toggle scan chains, the plurality of test cubes, and the predetermined size and toggle rate for the hold-toggle pattern.

18. The one or more non-transitory computer-readable media recited in claim 17 , wherein the determining the full-toggle scan chains comprises:

determining the toggle ranges for each of the scan chains for the each of the test cubes;

determining chain-reduced toggle ranges by combining the toggle ranges for each of the scan chains for the each of the test cubes based on the predetermined size for the hold-toggle pattern;

determining reduced toggle ranges for the each of the test cubes by combining the chain-reduced toggle ranges based on the predetermined toggle rate for the hold-toggle pattern; and

determining the full-toggle scan chains based on scan chains of which the chain-reduced toggle ranges cannot be combined into the reduced toggle ranges due to the predetermined toggle rate for the hold-toggle pattern and the number of device inputs available for full-toggle scan chains.

19. The one or more non-transitory computer-readable media recited in claim 15 , wherein the determining operational mode information and a hold-toggle pattern comprises:

determining the hold-toggle pattern using a relaxation algorithm and based on the plurality of test cubes and the predetermined size and toggle rate for the hold-toggle pattern.

20. The one or more non-transitory computer-readable media recited in claim 19 , wherein the determining the hold-toggle pattern comprises:

replacing test cubes having conflicts with a selected intermediate hold-toggle pattern generated by the relaxation algorithm with test cubes generated based on the selected intermediate hold-toggle pattern.

21. The one or more non-transitory computer-readable media recited in claim 19 , wherein the determining operational mode information and a hold-toggle pattern further comprises:

determining the full-toggle scan chains based on test cubes having conflicts with an intermediate hold-toggle pattern selected by the relaxation algorithm and the number of device inputs available for full-toggle scan chains.

22. The one or more non-transitory computer-readable media recited in claim 21 , wherein the determining the full-toggle scan chains comprises:

ranking scan chains based on the test cubes having conflicts with the selected intermediate hold-toggle pattern; and

using the ranked scan chains and the number of device inputs available for full-toggle scan chains to determine the full-toggle scan chains.

23. The one or more non-transitory computer-readable media recited in claim 19 , wherein the determining the hold-toggle pattern comprises:

selecting an intermediate hold-toggle pattern from intermediate hold-toggle patterns generated by the relaxation algorithm based on a specified bits-related cost function.

24. The one or more non-transitory computer-readable media recited in claim 15 , wherein the device is an expander in a decompressor.

25. The one or more non-transitory computer-readable media recited in claim 15 , wherein the generating test patterns comprises generating compressed test patterns.

26. The one or more non-transitory computer-readable media recited in claim 25 , wherein the compressed test patterns are test patterns encoded for EDT (embedded deterministic test)-based decompressors.

27. The one or more non-transitory computer-readable media recited in claim 15 , wherein the predetermined size for the hold-toggle pattern is 40 bits or fewer, the predetermined toggle rate for the hold-toggle pattern is two times the scan chain shift toggle rate limit, and the predetermined maximum number of device inputs for the full-toggle scan chains is 2.

28. The one or more non-transitory computer-readable media recited in claim 15 , wherein the plurality of faults are a subset of originally targeted faults.