Design for Self-Test SRL Implementation
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
This structure combines both signature compressor and pseudo-random generators in each SRL (shift register latch) string using standard L3 latches. The only additional circuitry required is Exclusive-OR (XOR) gates between SRL stages which provide the compression function (Fig. 1). In principle, each L3 latch is used to hold the vector results, while the L2 latch holds the seed of the current vector. These two are Exclusive-ORed together to produce the new vector. The first SRL stage on each chip is driven by the XOR of the feedbacks Fig. 3). (Note: Restricting feedback circuitry to the chip level obviates the use of substrate wiring and chip I/O's to accomplish this on a larger scale.) The test operation begins by initializing the SRL string(s) in the following manner.