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This article proposes a Built-In Self-Test (BIST) method to accurately measure the combinatorial circuit delays on an FPGA. The flexibility of the on-chip clock generation capability found in modern FPGAs is employed to step through a range of frequencies until timing failure in the combinatorial circuit is detected. In this way, the delay of any combinatorial circuit can be determined with a timing resolution of the order of picoseconds. Parallel and optimized implementations of the method for self-characterization of the delay of all the LUTs on an FPGA are also proposed. The method was applied to Altera Cyclone II and III FPGAs . A complete self-characterization of LUTs on a Cyclone II was achieved in 2.5 seconds, utilizing only 13kbit of block RAM to store the results. More extensive tests were carried out on the Cyclone III and the delays of adder circuits and embedded multiplier blocks were successfully measured. This self-measurement method paves the way for matching timing requirements in designs to FPGAs as a means of combating the problem of process variations.

Electron ic En g in eerin g , Im perial C olleg e L on d on , U K B r a n don B lodg et, J a m es A n der s on Pa tr ick L y s a g h t X ilin x , In c., 2 1 0 0 L og ic Driv e, S an J os e, C A 9 5 1 2 4 , U S A T ob ia s B eck er U n iv ers ität K arls ru h e (T H ), K ais ers traß e 1 2 -7 6 1 3 1 K arls ru h e, G erm an y ABSTRACT Modular systems implemented on Field-Programmable G ate A rrays c an benefi t from being able to load and unload modules at run-time, a c onc ept th at is of muc h interest in th e researc h c ommunity. W h ile dynamic partial rec onfi guration is possible in V irtex series and S partan series FPG A s, th e c onfi guration arc h itec ture of th ese dev ic es is not amenable to modular rec onfi guration, a limitation w h ic h h as relegated researc h to th eoretic al or c ompromised resourc e alloc ation models. In th is paper tw o meth ods for implementing modular dynamic rec onfi guration in V irtex FPG A s are c ompared and c ontrasted. T h e fi rst meth od offers simplic ity and fast rec onfi guration times, but limits th e geometry and c onnectiv ity of th e system. T h e sec ond meth od, rec ently dev eloped by th e auth ors, enables modules to be alloc ated arbitrary areas of th e FPG A , bridging th e gap betw een th eory and reality and unloc k ing th e latent potential of partial rec onfi guration. T h e later meth od h as been demonstrated in th ree applic ations. . I N TRO D U CTI O NT h e transistor density of Field Programmable G ate A rrays h as reac h ed a lev el w h ere an entire system may be implemented w ith in a single dev ic e. A c omplex system is generally c omposed from many func tionally disc rete modules, w h ic h are c onnec ted to form a c oh erent w h ole. In some c ases w h ere th e req uirements on th e system are time-v ariant, not all modules need to operate c onc urrently. A n unused module resident in th e FPG A w ill w aste pow er, area and c ost, and th erefore it w ould be adv antageous if modules are able to be loaded only w h en an applic ation is inv ok ed and remov ed again onc e th e applic ation h as terminated.T h ere h as been a large amount of researc h in th e area of dynamic modular systems in FPG A s [1 , 2 , 3 , 4 , 5 ]. T h ese are predic ated on th e property of dynamic partial rec onfi guration, h ow ev er module-based rec onfi guration h as not been intrinsic ally supported in FPG A s sinc e th e demise of th e * The authors wish to thank Jean Belzile, Normand Leclerc, Pierre-A ndré M eunier and D av id R ob erg e from IS R Technolog ies for their inv aluab le contrib utions, and also Peter C heung for his critiq ue of this p ap er.X ilinx 6 2 0 0 series. W h ile th e V irtex and S partan series of FPG A s are partially rec onfi gurable, th e essentially linear organisation of th e c onfi guration memory is not amenable to th e implementation of module-based systems w ith tw odimensional fl oorplans. A s a result researc h h as tended to be eith er th eoretic al, or sev erely c irc umsc ribed, typic ally by reduc ing th e resour...

Reliability and process variability are serious issues for FPGAs in the future. Fortunately FPGAs have the ability to reconfigure in the field and at runtime, thus providing opportunities to overcome some of these issues. This paper provides the first comprehensive survey of fault detection methods and fault tolerance schemes specifically for FPGAs, with the goal of laying a strong foundation for future research in this field. All methods and schemes are qualitatively compared and some particularly promising approaches highlighted.