Method of diagnosing multiple stuck‐at‐faults in combinational circuits

Abstract

To reduce VLSI turnaround t i m e and c o s t , an e f f i c i e n t f a u l t d i a g n o s i s method must be developed.Electron-beam probing, which allows observation of t h e s i g n a l values w i t h i n a chip, i s one of t h e promising approaches f o r f a u l t diagnosis. However, i t i s s t r o n g l y d e s i r e d t h a t t h e number of probes be reduced; otherwise, a g r e a t d e a l of e f f o r t r e s u l t s . The electron-beam probing, guided by deduction based on i m p l i c a t i o n s of i n t e r n a l s i g n a l v a l u e s [ 6 ] , i s considered one of t h e e f f e c t i v e s o l u t i o n s t o t h i s problem. Here t h i s idea i s b u i l t upon by adding preprocessing t o f u r t h e r reduce t h e number of probes and postprocessing t o improve t h e diagnosis r e s o l u t i o n . The method proposed e f f i c i e n t l y diagnoses m u l t i p l e stuck-at f a u l t s i n combinational c i r c u i t s . Using computational experiments i t i s a l s o shown t h a t almost a l l of t h e f a u l t s are diagnosed by probing about 15 p e r c e n t of t h e n e t s when t e s t p a t t e r n s f o r d e t e c t i n g s i n g l e stuck-at f a u l t s are used. 1. I n t r o d u c t i o n Although more and more d i f f e r e n t kinds of VLSI products are being produced, t h e small volume of each type demands development of an e f f i c i e n t f a u l t d i a g n o s i s method i n o r d e r t o reduce both turnaround t i m e and cost. I n t h e development phase t h e capabili t y t o diagnose m u l t i p l e f a u l t s is e s p e c i a ll y d e s i r e d . A number of d i a g n o s i s methods have s o f a r been proposed. However, each h a s some p r a c t i c a l use problems. I n t h e f a u l t dic-21 t i o n a r y method, which s t o r e s t h e abnormal o u t p u t s f o r v a r i o u s f a u l t s i n a d i c t i o n a r y and compares them a g a i n s t t h e observed outp u t s [ 11 , t h e s i z e of t h e d i c t i o n a r y becomes very l a r g e when t h e c i r c u i t s become l a r g e . When m u l t i p l e f a u l t s are considered, t h i s problem becomes prominent and i t i s not p r a c t i c a l . The cause-effect a n a l y s i s method [ 2 ] , i n which f a u l t s are i n f e r r e d from t h e observed o u t p u t v a l u e s without u s i n g a d i c t i o na r y , does not g u a r a n t e e maximum r e s o l u t i o n . which can be probed a t one t i m e i s l i m i t e d , a c o n s i d e r a b l e amount of t i m e i s necessary t o probe a l l of t h e n e t s . Moreover, probing n e t s t h a t are not on t h e t o p l a y e r r e q u i r e s much e f f o r t . A method combining t h e b a s i c o p e r a t i o n of t h e c a u s e -e f f e c t a n a l y s i s method and t h e probing [ 6 ] seems t o have t h e p o s s i b i l i t y of becoming a n e f f i c i e n t diagn o s i s method. r e q u i r e d . c u i t s based on previous r e s e a r c h [ 6 ] and by adding t o i t a preprocessing t o reduce t h e number of probes and a postprocessing ...

Multiple fault diagnosis in combinational circuits using sensitizing input‐pairs

“…However, the post-processes such as diagnosis by adaptive tests and probing internal lines are required in order to identify the faulty line exactly. If we probe internal lines, our method can obtain higher resolution than that of the method in (6) since we can identify Here the probing rate is defined as the ratio of the number of probed lines to the number of all lines [6].…”

“…When the D-frontier is propagated to a primary output, the current primary inputs are added to the set of diagnostic tests and a return to (4-1) is made after selecting the next D-frontier signal line from Stuck. If Stuck is empty, then go to (6). When the D-frontier signal line is another line, return to (4-1).…”

“…Therefore, a guided-probing method by an electron-beam tester [4] was proposed. By using a test set under a single stuck-at fault model, Yamada et al presented a practical method to multiple fault diagnosis using deduction and probing algorithms [6]. Electron-beam probing is, however, a time-consuming and laborious task.…”