Abstract: A method for controlling a gating circuit of an electronic system incorporating a scan architecture complying with IEEE Standard 1149.1 such that the gating circuit applies mutually exclusive signals to, for example, a decoded multiplexer. The gating circuit receives input signals from flip-flops that are part of a scan chain, is selectively controllable by a control signal to transmit predetermined mutually exclusive signals to the select inputs of the multiplexer during a scan mode. Alternatively, the gating circuit is controllable by the control signal to pass the input signals to the multiplexer in a normal operation or test mode. A mutual exclusivity circuit is provided to generate the control signal. During the scan mode, the control signal is generated at a first logic level such that the gating circuit transmits the predetermined mutually exclusive signals to the multiplexer while test values are being scanned into the flip-flops.

Abstract: A circuit is disclosed which allows an IN-Test to be performed on an integrated circuit (IC) without having to stop the external clock sources by disabling the IC's internal phase-locked loops. Information indicative of the IC's clock mode and of the desired stop mode is contained within the IC's clock control register. In one embodiment, the internal clocks may be stopped in either of three stop modes while operating in one of three clock modes. When it is desired to stop the IC's internal clocks, the clock control register provides a stop instruction signal STOP.sub.-- INSTR to a clock control circuit which, depending upon the particular stop mode and clock mode encoded in signal STOP.sub.-- INSTR by the clock control register, asserts a enabling signal to a disable clock circuit.

Abstract: A circuit for locally ensuring mutual exclusivity of selected signals during scan testing is coupled between an IEEE 1149.1 TAP controller and a conventional gating circuit. The mutual exclusivity circuit includes an AND-gate, an inverter, a first scan flip-flop and a second scan flip-flop. The first and second flip-flops have their scan-input leads hardwired to receive logic "1" and logic "0" signals, respectively. The first flip-flop also has its data input lead hardwired to receive a logic "0" signal. During the scan mode, the AND-gate receives a conventional rst.sub.-- tri.sub.-- en signal from the TAP controller. Thus, the AND-gate outputs a local.sub.-- rst.sub.-- tri.sub.-- en signal identical to the rst.sub.-- tri.sub.-- en signal. After the test pattern is scanned in, the rst.sub.-- tri.sub.-- en signal transitions to a logic "1" level, causing the local.sub.-- rst.sub.-- tri.sub.

Abstract: A circuit for coupling a LIC driver to a IEEE 1149.1 boundary scan implementation includes a logic circuit that converts the data and oe signals of the IEEE 1149.1 specification to test "q.sub.-- up" and "q.sub.-- dn" signals meeting the requirements of the LIC driver. These test "q.sub.-- up" and "q.sub.-- dn" signals are selectively provided to the LIC driver during boundary scan testing of the output driver. In a further refinement, the logic circuit also converts functional q.sub.-- up and q.sub.-- dn signals provided by the circuit under test to the data and oe signals of the IEEE 1149.1 specification. The logic circuit allows the widely used IEEE 1149.1 boundary scan standard to be used with LIC drivers. The resulting compatibility simplifies the testing and use of the LIC drivers, and provides a new boundary scan standard for use with LIC drivers that is compliant with the IEEE 1149.1 standard.

Abstract: A method for coupling a linear impedance control (LIC) type output driver to IEEE 1149.1 boundary scan circuitry includes entering a boundary scan load mode to load a test pattern into a chain of boundary scan registers (BSRs). The test pattern includes values corresponding to output enable and data signals according to the IEEE 1149.1 standard. Then these data and output enable signals from the BSRs are converted into test "q.sub.-- up" and "q.sub.-- dn" signals meeting the requirements of the LIC driver. These test "q.sub.-- up" and "q.sub.-- dn" signals are selectively provided to the LIC driver during boundary scan testing of the LIC driver. In a further refinement, the method enters a boundary scan capture mode to capture the response (i.e., the functional q.sub.-- up and q.sub.-- dn signals) of the circuit under test to input test patterns shifted into the BSRs. The functional q.sub.-- up and q.sub.-- dn signals are converted into response data and oe signals complying with the IEEE 1149.

Abstract: Circuits and methods of testing an integrated circuit die are disclosed. Active logic setting circuits are incorporated into input cells of a die. During testing, the active logic setting circuits weakly drive the input cells to a definite logic level. Therefore, the necessity of connecting probes to all of the input pads to prevent floating signals in the die is eliminated. Furthermore, during normal operations the active logic setting circuits have little or no effect on the performance of the die.

Abstract: A control circuit to stop an integrated circuit internal clock includes a signal distribution trace connected to a clock stop pipeline. The signal distribution trace creates a large phase delay signal for a first integrated circuit internal clock cycle which activates the clock stop pipeline, and a small phase delay signal for a final integrated circuit internal clock cycle that deactivates the clock stop pipeline. The clock stop pipeline includes a first circuit component to generate an intermediate stop instruction in response to a clock stop command and the large phase delay signal of the first integrated circuit internal clock cycle. The intermediate stop instruction proceeds through the clock stop pipeline in response to clock cycles following the first clock cycle.

Abstract: An integrated circuit includes a first metal layer with first layer identification signal writing circuitry connections to produce first metal layer circuit identification signals. The integrated circuit also has a second metal layer with second layer identification signal writing circuitry connections to produce second metal layer circuit identification signals. Logic circuitry in the first metal layer has input connections to the first layer identification signal writing circuitry connections and the second layer identification signal writing circuitry connections. The logic circuitry combines the first metal layer circuit identification signals and the second metal layer circuit identification signals to produce a circuit identification number. The value of the circuit identification number can be changed by altering the first layer identification signal writing circuitry connectors or the second layer identification signal writing circuitry connections.

Abstract: High speed scan testing is facilitated by pipelining or distributing a scan enable signal to scan circuits through a distribution network. The pipeline is formed from a plurality of scan enable distribution circuits residing on an integrated circuit to be scan tested. Preferably, before reaching the scan circuits, the scan enable signal passes through an equal number of the scan enable distribution circuits. The distribution network of the scan enable distribution circuits take a multitude of forms. The invention allows at-speed toggling of a scan enable signal as well as shifting of test data at functional system frequencies, while maintaining compatibility with test modes such as IEEE Standard 1149.1. The invention is also capable of supporting skewed-load and broad-side delay test modes.

Abstract: A logic signal validity verifier for use in determining the validity of the logic states of a group of logic signals includes an inactive signal fault monitor for determining when all of the logic signals are in an inactive signal state and an active signal fault monitor for determining when more than one of the logic signals are in an active signal state. Where the logic signals are differential, the logic signal validity verifier further includes a differential signal fault monitor for determining when corresponding pairs of the differential logic signals are in the same active or inactive signal state.

Abstract: A method and apparatus is disclosed for advantageously implementing a full boundary scan test of input and bi-directional paths of an integrated circuit. The present invention provides a full boundary scan test capability with practically no degradation of speed of operation during normal operation of the integrated circuit. Within the integrated circuit under test, boundary scan registers are coupled to each input and bi-directional pin. When placed in a test mode, the corresponding output drivers are tristated for every bi-directional pin of the integrated circuit under test. Then the values of a test signal vector asserted on the pins of the integrated circuit are captured by the boundary scan registers. These captured values are retrieved and output from the integrated circuit so that they can be compared to the asserted test signal vector.

Abstract: Two related methods and apparatus for determining a binary constant to be output from embedded memory arrays into system logic of an integrated circuit when the system logic is being tested, that maximizes improvement to fault coverage of the system logic, are disclosed. The present invention has particular application to digital system testing. The fault coverage of the system logic is improved due to its controllability and observability are indirectly enhanced by the enhanced controllability of the embedded memory arrays. The first related method and apparatus determines the binary constant based on a testability measure selected for the system logic. The second related method and apparatus determines the binary constant based on results from automated test patterns generation for the integrated circuit.

Abstract: A method and apparatus for improving the testability of system logic of an integrated circuit having embedded memory arrays is disclosed. The embedded memory arrays are coupled to a binary constant generation and selection circuit which is also coupled to the system logic. During a test mode, the selection circuit sends a binary constant to the system logic in lieu of normal operational data output from the memory arrays. The system logic is tested while the binary constant is continuously applied.