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: A method and apparatus for providing automatic verification of the kernel circuitry of a microprocessor-based system in which the microprocessor (.mu.P) include an instruction prefetch feature. During testing by memory emulation, the memory addresses accessed by the .mu.P are evaluated as to type of access, address and data size in accordance with a test program and a corresponding checking table to determine if such accesses are consistent with a funtional .mu.P of the same type. Other data structures such as flags and pointers are provided to enhance the verification operation and use of the checking table.

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.

Abstract: A method and system for testing and troubleshooting microprocessor-based electronic systems employs memory emulation techniques as well as other techniques to provide complete functionality tests and fault location. Fine-resolution sync pulses may be generated at preselected time positions during a bus cycle of interest to facilitate full troubleshooting fault isolation. Other features include bus testing using memory emulation techniques, using the chip select line of ROMs to encode test results, and techniques that keep a target microprocessor functioning in a system in which the kernel is dead.

Abstract: Circuit faults in an electronic system are isolated by a programmed computer that guides a technician node-by-node on a unit under test (UUT), such as a circuit board, to the source of a failure. Stimulus pattern signals are applied to the circuit, and responses at the circuit nodes are made by a measurement probe under the hand of the technician. As each node is probed, a stimulus pattern signal tailored for testing that node is applied to the UUT. The measured response is compared to a predetermined response corresponding to an operational UUT to generate a failure accusation or recommend the next node to be probed. The computer is programmed to expedite the search for the source of the failure by displaying to the technician clues which define the circuit nodes most apt to be defective as a result of preliminary functional testing of the UUT.