A technique of decreasing the number of test patterns required to test a MOSFET module and/or provide the ability to test elements on the module which can not be tested by conventional test techniques. Conventionally, test patterns are applied to the input pins of a MOSFET module and the output monitored at the output pins of the module. Interwoven with the normal test pattern testing is the application of a serial test pattern to selected elements on the module. The serial test pattern is applied to a single input pin on the module and a serial test pattern is stored in a shift register which is on the module. Each of the stages of the shift register are used to control or monitor an element or point which may be otherwise inaccessible or untestable and the shift register is also utilized in an output mode to provide an indication serially on a single output pin as to the functioning of the points accessed on the module. The sequence then is to input onto a single input pin a serial test pattern for testing, controlling or monitoring various elements or nets on the module; reload the shift register in accordance with the test results; and then serially shift the contents of the shift register out onto the single output pin while monitoring this output to determine whether the elements or nets are functioning properly. In addition, while the serial test pattern is applied the output appearing at the output pins of the module may be monitored.
A merged AND/OR array PLA is disclosed wherein the merger is accomplished by forming the gates of the FET devices in the AND array by means of an upper conductor layer and the gates of the FET devices in the OR array, which are connected to the drain of the devices in the AND array, by means of lower level conductor layer, so that the devices are contiguous. The PLA structure uses a polysilicon layer for interconnection between AND array FET drains and OR array FET gates, with the AND array FETs or OR array FETs being intermixed in a single array. The OR array outputs are oriented vertically, alternating between the AND product terms and ground diffusions. All PLA outputs are oriented vertically within the same array. A testing technique and special testing circuitry is disclosed which makes use of the existing bit partitioning input buffer as the source of test patterns and the existing output latches as the storage for the test response bits for individually testing both the AND components and the OR components in the merged array PLA.
Test circuitry is disclosed for testing a circuit module with a high probability of error detection. The circuitry is relatively simple and is therefore readily adaptable for integration with the module to be tested thereby providing effective fault detection capability at the system level. A pseudo-random pattern generator provides the logic to be tested with a series of parallel test inputs. The output from the logic at the end of each cycle within the test sequence is multiplexed into a sequential bit stream which forms the input to a cyclic code generator. After the test sequence has been run for a predetermined number of cycles, the output of the cyclic code generator is compared with a hardwired constant representative of the output of a good unit. Inasmuch as the cyclic code generator is not reset between cycles, two levels of output data reduction are provided -- within a single test cycle and within a sequence of cycles. If the comparison indicates a mismatch, an error signal is output.
A shift register connected to elementary gates is added to a digital network to form a fault simulator. The shift register and the additional gates can select a connection from the digital network and simulate a fault on the selected connection. Connection selection is done at a speed comparable to that at which the digital network operates and fault simulation is nondestructive. By resetting the shift register the fault simulator performs as if the digital network were fault-free. To simulate certain faults in the digital network a predetermined fault injection pattern for the faults to be simulated is entered into the shift register.
A test simplifying circuit is based on a compact test method which is a test method for applying a test pattern series generated from a random pattern generator to a digital circuit to be tested and at the same time for compressing a response output of the to-be-tested circuit by use of a data compactor, and determining the result of data compression. The memory circuits and input/output circuits originally contained in an integrated circuit are used as the random pattern generator and data compactor used for the test, and the random pattern generator and data compactor are reconstructed by the memory circuits and the input/output circuits.
A boundary-scan-testing integrated circuit adapted to both a functional test of an entire IC chip and a parametric test for input and output buffers, connected to pads of the IC chip, in a periphery cell area of the IC chip. First memory circuits are respectively formed in an input buffer portion, an output buffer portion, and a bidirectional buffer portion, which are provided in the peripheral cell area of the IC chip. Second memory devices control ON/OFF operations of active elements, formed in the input buffer portion and the bidirectional buffer portion, for supplying a pad potential. Third memory devices control ON/OFF operations of tristate buffers of the output buffer portion and the bidirectional buffer portion. The first, second, and third memory devices are serially connected, thereby constituting a shift register controlled by a first control signal. First and second data selectors are operated by data output from the shift register, thereby controlling input and output buffers, and resistors for determining a potential of pads.
