Abstract: An optical fiber propagation time measurement circuit. A light pulse is iteratively transmitted into a near end of a fiber under test (FUT) at a predetermined frequency and detected at a far end of the FUT after a propagation time. A repetitive propagation signal having a predetermined amplitude and a width corresponding the propagation time is developed by detection circuitry. The d.c. voltage average of the propagation signal is determined and used to compute the propagation time since the ratio of the d.c. voltage average to the predetermined amplitude is equal to the ratio of the propagation time to the period of the light pulses.

Abstract: An improved testing apparatus and method for testing the kernel of a microprocessor based unit under test (UUT) in which connection to the UUT is made at both the memory connection socket and at the microprocessor with the microprocessor being in place and active in the UUT. The apparatus and method permits substantially full diagnostics of the kernel to be carried out in a systematic and automated manner in which the requirement of manual probing of the UUT is minimized. Connections at the microprocessor permit the development of high resolution sync signals for verification and evaluation of test results. The testing protocol implemented in the method includes the use of testing primitives which permit the development of a signature for each address and data bus line for the identification of the type as well as the location of any faults discovered by the apparatus.

Abstract: An apparatus, method and data structure for validating the data bus of a microprocessor-based unit under test in which bit patterns having half as many bits as the width of the data bus are applied to the data bus along with another bit pattern which is either the complemented or true replication of the bit pattern. Evaluation of the resulting bit patterns on the data bus permits a validation of the entire width of the data bus which, if no faults are reported, obviates not only probing of the data bus by the operator but data bus diagnosis, as well. A particular data structure of a preferred bit pattern sequence avoids any fault on any data line being reported as a pass.