Testing of one-dimensional (1-D) unilateral iterative logic arrays (ILA's) of combinational cells with constant test vectors is studied and the concept of one repetition length (ORL) within the tests used for testing C-testable arrays is described. The impact of ORL on the test set size and the design of the test generator are discussed. ORL can dramatically reduce the on-chip test generator size with a negligible increase in the test set size. ORL, coupled with a single distinguishing sequence (DS) for ILA's with cell vertical outputs has proved to be attractive in terms of both reduced test set size and reduced test generator size. ORL testability can be used for C-testable arrays with single faulty cell and multiple faulty cells. The technique for using a single linear finite state machine (LFSM) for generating the necessary deterministic test patterns followed optionally by pseudorandom patterns from the same automaton is discussed. Use of an LFSM as a built-in test generator for only deterministic tests for 1-D ILA's is covered. With ORL, a compact LFSM based built-in self test (BIST) generator can deliver the test vectors to all the cells in the array. The exact probability distribution equation has been developed for additional bits needed to map a nonlinear machine (FSM) definition into a LFSM definition. The distribution clearly shows that the expected number of additional bits is very small, often zero.>

Linear Finite State Machine for One Dimensional (1D) Iterative Logic Arrays (ILAs) is described. The technique for modifying the Linear Feedback Shift Register (LFSR) based test generator called Linear Finite State Machine (LFSM) for deterministic test pattern generation is discussed and extended for generating the test vectors for 1D unilateral ILAs. One Repetition Length (ORL) of C-testable ILAs and unique characteristics of the C-testable test patterns are used for the compact design of the LFSM based at-speed Built-in Self Test (BIST). Such LFSM based BIST occupies small silicon area, simplifies the design of the controller and does at-speed testing of the ILAs. This results in reduced time and cost of testing. In addition, the exact probability distribution equations are developed for additional bits needed to map a Finite State Machine (FSM) into an LFSM. The distribution clearly shows that the expected number of additional bits is very small, often zero. The probability distribution equations are equally valid for any LFSR based test generator for other circuits.>