The present invention relates in general to an apparatus and method for injecting faults on the pins of an integrated circuit employed to perform a logical function.
In the testing of the error detection section of a device employing integrated circuits, it is desirable to be able to create error conditions on the inputs and outputs of the integrated circuits employed in the device. The ability to create such error conditions is also useful in the development and testing of diagnostic programs used in data processing systems to diagnose faults in the data processor and attached input/output devices.
Testing apparatuses for dynamically injecting errors in a data processing system have previously been proposed, for example, in East, D. G., et al., Error Injector for Testing a Data Processing Unit, in IBM Tech. Disc. Bull., 17 (6): p. 1691, Nov. 1974, and also in Maiden, D. W., et al., Error Injector Probe, in IBM Tech. Disc. Bull., 18 (1): p. 7, June 1975. In such apparatuses, it will be realized that an error may only be injected at one point in a device once the testing apparatus is connected. Further, the occurrence and location of an error cannot be controlled programatically.
Computer controlled circuit testers for applying predetermined signals to individual pins to which the circuit to be tested is connected have also been proposed, for example, in U.S. Pat. No. 3,872,441 by George William Cailow, filed Nov. 29, 1972. In such an apparatus, it will be realized that errors cannot be applied to circuits that are performing a logical function in the device of which they are an element.
Testing units for insertion in a circuit with a circuit board, including an extender board containing circuits for transmitting and receiving data, have been proposed, for example, in U.S. Pat. No. 3,904,861 by John E. McNamara, filed Mar. 13, 1974. In such an apparatus, the circuit board is removed and the extender board is placed in circuit with the circuit board. The circuit board may then be tested with a duplication of system conditions, the circuits in the extender board receiving and transmitting data. In such an apparatus, it will be realized that the functions performed by the circuits on the extender board are fixed by the hardware and therefore signals cannot be selectively altered or passed through without modification. Further, the apparatus is designed to operate only on signals entering and leaving the circuit board through the circuit board's connection with the connector block the circuit board normally plugs into. As a consequence, no modification to signals passing between circuits mounted on the circuit board can be performed.
Therefore, it is an object of the present invention to provide an error injection apparatus which can simulate error conditions in an integrated circuit which is an in-line component of an electronic circuit.
Another object of the present invention is to provide an error injection apparatus capable of simulating errors on multiple input or output pins of an integrated circuit.
It is a further object of the present invention to provide an error injection apparatus capable of varying the input or output pins of an in-line integrated circuit which have simulated errors applied to them without the necessity of rewiring the error injection apparatus.
It is an additional object of the present invention to provide a programmatically controlled apparatus and method for simulating errors on input or output pins of an integrated circuit while the integrated circuit is performing its normal logical functions as an in-line component of an electronic circuit.