Irith Pomeranz

COMPACTEST: a method to generate compact test sets for combinational circuits

Heuristics to aid the derivation of small test sets that detect single stuck-at faults in combinational logic circuits are proposed. The heuristics can be added to existing test pattern generators without compromising fault coverage. Experimental results obtained by adding the proposed heuristics to a simple PODEM procedure and applying it to the ISCAS-85 and fully-scanned ISCAS-89 benchmark circuits are presented to substantiate the effectiveness of the proposed heuristics. >

Techniques for minimizing power dissipation in scan and combinational circuits during test application

Reduction of power dissipation during test application is studied for scan designs and for combinational circuits tested using built-in self-test (BIST). The problems are shown to be intractable. Heuristics to solve these problems are discussed. We show that heuristics with good performance bounds can be derived for combinational circuits tested using BIST. Experimental results show that considerable reduction in power dissipation can be obtained using the proposed techniques.

Transient-fault recovery using simultaneous multithreading

We propose a scheme for transient-fault recovery called Simultaneously and Redundantly Threaded processors with Recovery (SRTR) that enhances a previously proposed scheme for transient-fault detection, called Simultaneously and Redundantly Threaded (SRT) processors. SRT replicates an application into two communicating threads, one executing ahead of the other. The trailing thread repeats the computation performed by the leading thread, and the values produced by the two threads are compared. In SRT, a leading instruction may commit before the check for faults occurs, relying on the trailing thread to trigger detection. In contrast, SRTR must not allow any leading instruction to commit before checking occurs, since a faulty instruction cannot be undone once the instruction commits.To avoid stalling leading instructions at commit while waiting for their trailing counterparts, SRTR exploits the time between the completion and commit of leading instructions. SRTR compares the leading and trailing values as soon as the trailing instruction completes, typically before the leading instruction reaches the commit point. To avoid increasing the bandwidth demand on the register file for checking register values, SRTR uses the register value queue (RVQ) to hold register values for checking. To reduce the bandwidth pressure on the RVQ itself, SRTR employs dependence-based checking elision (DBCE). By reasoning that faults propagate through dependent instructions, DBCE exploits register (true) dependence chains so that only the last instruction in a chain uses the RVQ, and has the leading and trailing values checked. SRTR performs within 1% and 7% of SRT for SPEC95 integer and floating-point programs, respectively: While SRTR without DBCE incurs about 18% performance loss when the number of RVQ ports is reduced from four (which is performance-equivalent to an unlimited number) to two ports, with DBCE, a two-ported RVQ performs within 2% of a four-ported RVQ.

Preferred Fill: A Scalable Method to Reduce Capture Power for Scan Based Designs

When the response to a test vector is captured by state elements in scan based tests, the switching activity of the circuit may be large resulting in abnormal power dissipation and supply current demand. High supply current may cause excessive supply voltage drops leading to larger gate delays which may cause good chips to fail tests. This paper presents a scalable approach called Preferred Fill to reduce average and peak power dissipation during capture cycles of launch off capture delay fault tests. Experimental results presented for benchmark and industrial circuits demonstrate the effectiveness of the proposed method

COMPACTEST: A METHOD TO GENERATE COMPACT TEST SETS FOR COMBINATIONAL CIRCUITS

Heuristics to aid the derivation of small test sets that detect single stuck-at faults in combinational logic circuits are proposed. The heuristics can be added to existing test pattern generators without compromising fault coverage. Experimental Tesults obtained by adding the proposed heuristics to a simple PODEM procedure and applying it to the ISCAS-85 and ISCAS-89 benchmark circuits are presented to substantiate the effectiveness of the proposed heuristics.

Cost-effective generation of minimal test sets for stuck-at faults in combinational logic circuits

This paper presents new cost-effective heuristics for the generation of minimal test sets. Both dynamic techniques, which are introduced into the test generation process, and a static technique, which is applied to already generated test sets, are used. The dynamic compaction techniques maximize the number of faults that a new test vector detects out of the yet-undetected faults as well as out of the already-detected ones. Thus, they reduce the number of tests and allow tests generated earlier in the test generation process to be dropped. The static compaction technique replaces N test vectors by M<N test vectors, without loss of fault coverage. During test generation, we also find a lower bound on test set size. Experimental results demonstrate the effectiveness of the proposed techniques.

On static compaction of test sequences for synchronous sequential circuits

We propose three static compaction techniques for test sequences of synchronous sequential circuits. We apply the proposed techniques to test sequences generated for benchmark circuits by various test generation procedures. The results show that the test sequences generated by all the test generation procedures considered can be significantly compacted. The compacted sequences thus have shorter test application times and smaller memory requirements. As a by product, the fault coverage is sometimes increased as well. More importantly, the ability to significantly reduce the length of the test sequences indicates that it may be possible to reduce test generation time if superfluous input vectors are not generated.

Cost-Effective Generation of Minimal Test Sets for Stuck-at Faults in Combinational Logic Circuits

New cost-effective heuristics for the generation of small test sets are introduced, and heuristics proposed previously are enhanced. An improved procedure is also proposed for computing independent fault sets which are used to selecet target faults in test generation. The procedure results in large lower bounds on the minimum test set size. Experimental results of test generation demonstrate the effectiveness of the heuristics.

3-weight pseudo-random test generation based on a deterministic test set for combinational and sequential circuits

A method for weighted pseudorandom test generation based on a deterministic test set is described. The main advantages of the method described over existing methods are: (1) only three easily generated weights (0, 0.5 and 1) are used, (2) a minimum number of shift register cells is used, thus leading to minimal hardware for built-in-test applications, and (3) the weights are selected to allow the same coverage of target faults attained by the deterministic test set to be attained by weighted random patterns. The weights are computed by walking through the range of test generation approaches from pure random at one extreme to deterministic at the other extreme, dynamically selecting the weight assignments to correspond to the remaining faults at every stage. Hardware suitable for the generation of random patterns under the proposed method is described. The method is suitable for both combinational and sequential circuits. Experimental results are provided for ISCAS-85 and MCNC benchmark circuits. >

On test data volume reduction for multiple scan chain designs

We consider issues related to the reduction of scan test data in designs with multiple scan chains. We propose a metric that can be used to evaluate the effectiveness of procedures for reducing the scan data volume. The metric compares the achieved compression to the compression which is intrinsic to the use of multiple scan chains. We also propose a procedure for modifying a given test set so as to achieve reductions in test data volume assuming a combinational decompressor circuit.