Abstract: Fault insertion circuits under programmable control and resident in an integrated circuit (LSI or VLSI) insert transient and intermittent fault classes in addition to a permanent fault class into functional logic on such integrated circuit. Specific fault types programmable for each fault class include a stuck-open fault and bridging faults both wired-AND and wired-OR. The programmable fault insertion circuitry on each integrated circuit interfaces directly or indirectly with a BIT maintenance controller. In addition to verifying test software, a fault tolerant system's error detection and recovery circuits may be verified by fault insertion testing using the transient and intermittent fault insertions.

Abstract: A microprogrammed control unit of an information processing system having a control sequencer with dual microprogram counters for performing microdiagnostics simultaneously with performing macroprograms. The microdiagnostics comprise background and operability tests, the background tests being interleaved with macroinstruction operations under the control of the two independent microprogam counters. The background tests are run during processor idle time and the operability tests are executed at processor turn-on. The organization of the microdiagnostics into a hierarchical structure allows the use of the same microprogrammed test module for both the background and operability microdiagnostic tests. A prediction/residual coding technique provides fault detection for address and data information within the control sequencer.

Abstract: Apparatus and method for providing programmable fault insertion circuitry in a large scale integrated (LSI) circuit device thereby eliminating the need for external switches or relays to create faults. A fault parameter word is stored in a register and the outputs of the register are decoded to select the fault condition to be inserted by an interfacing circuit to the logic being tested. Test vectors and the fault parameter word are generated by a controller coupled to the integrated circuit and a test response from the integrated circuit is examined by the controller.

Abstract: A control system for use with a welding machine controller is provided which senses the dynamic resistance of the weld being formed by the welding machine, and which generates appropriate signals indicating the condition of the weld, which signals may be used for automatically controlling the operation of the controller. The control system of the invention senses the power factor in the primary circuit of the welding transformer included in the welding machine which is a measure of the dynamic resistance of the weld being formed, and the control system produces signals indicating the dynamic resistance of the weld, which signals may be digitized to produce appropriate control signals for the controller.

Abstract: A precision resistance welding machine controller is provided which may be set to deliver welding power to each of a multiplicity of welding operations on a precisely controlled repeatable basis. The controller of the invention is modular in nature and is microprocessor controlled. The controller includes a master control module which is standard for all models, and the master control module incorporates certain control circuits including a circuit for assuring that an accurately controlled amount of power is delivered for each welding operation. This is achieved by providing precise phase angle control despite variations in line voltage, and line noise disturbances. The controller also includes a personality module which is constructed for a particular welding operation, and which is programmed to incorporate any selected number of steps to be performed in sequence by the welding machine controlled thereby in carrying out the particular welding operation.

Abstract: An interface circuit is provided for interconnecting an electronic controller to a contactor circuit which, in turn, controls the alternating current flow from an alternating current power source to controlled equipment, such as a resistance welding machine. The contactor circuit, for example, includes a pair of semiconductor switching devices, such as silicon controlled rectifiers (SCR)s, the two semiconductor switching devices are alternately rendered conductive during successive half-cycles of the alternating current power from the alternating current power source at times controlled by the controller for the controlled operation of the welding machine. The interface circuit includes means for monitoring the junction temperature of each of the semiconductor switching devices, and to provide an indication and a control effect should the junction temperature exceed a particular safe threshold.