摘要:
Disclosed are methods for utilizing programmable logic devices that contain at least one localized defect. Such devices are tested to determine their suitability for implementing selected designs that may not require the resources impacted by the defect. If the FPGA is found to be unsuitable for one design, additional designs may be tested. The test methods in some embodiments employ test circuits derived from a user's design to verify PLD resources required for the design. The test circuits allow PLD vendors to verify the suitability of a PLD for a given user's design without requiring the PLD vendor to understand the user's design.
摘要:
Described are methods for implementing customer designs in programmable logic devices (PLDs). The defect tolerance of these methods makes them particularly useful with the adoption of “nanotechnology” and molecular-scale technology, or “molectronics.” Test methods identify alternative physical interconnect resources for each net required in the user design and, as need, reroute certain signal paths using the alternative resources. The test methods additionally limit testing to required resources so devices are not rejected as a result of testing performed on unused resources. The tests limit functional testing of used resources to those functions required in the user designs.
摘要:
A circuit measures the signal propagation delay through a selected test circuit. The test circuit is provided with an inverting feedback path so that the test circuit and feedback path together form a free-running oscillator. The oscillator then automatically provides its own test signal that includes alternating rising and falling signal transitions on the test-circuit input node. These signal transitions are counted over a predetermined time period to establish the average period of the oscillator. Finally, the average period of the oscillator is related to the average signal propagation delay through the test circuit. One embodiment of the invention includes a phase discriminator that samples the output of the oscillator and accumulates data representing the duty cycle of that signal. The duty cycle can then be combined with the average period of the test signal to determine, separately, the delays associated with falling and rising edges propagating through the test circuit.
摘要:
A circuit separately measures a selected one of the rising-edge and falling-edge signal propagation delays through one or more circuits of interest. A number of synchronous components are configured in a loop so that they together form a free-running ring oscillator. Each synchronous component clocks a subsequent synchronous component in the ring; the subsequent synchronous component responds by clocking a later component in the ring and by clearing a previous component to prepare it for a subsequent clock. The oscillator thus produces an oscillating test signal in which the period is proportional to the clock-to-out delays of synchronous components. This proportionality provides an effective means for measuring the clock-to-out delays of those components. Other embodiments include additional asynchronous test circuit paths for which the associated signal propagation delays are of interest.
摘要:
Methods of utilizing partially defective PLDs, i.e., PLDs having localized defects. A partially defective PLD is tested for compatibility with a particular configuration bitstream. If the partially defective PLD is compatible with the bitstream (i.e., if the localized defect has no effect on the functionality of the design implemented by the bitstream), a product is made available that includes both the bitstream and the partially defective PLD. In some embodiments, the bitstream is stored in a memory device such as a programmable read-only memory (PROM). In some embodiments, the product is a chip set that includes the partially defective PLD and a separately-packaged PROM in which the bitstream has previously been stored. In some embodiments, the PROM is manufactured as part of the FPGA die.
摘要:
Disclosed are methods for utilizing programmable logic devices that contain at least one localized defect. Such devices are tested to determine their suitability for implementing selected designs that may not require the resources impacted by the defect. If the FPGA is found to be unsuitable for one design, additional designs may be tested. The test methods in some embodiments employ test circuits derived from a user's design to verify PLD resources required for the design. The test circuits allow PLD vendors to verify the suitability of a PLD for a given user's design without requiring the PLD vendor to understand the user's design.
摘要:
A circuit measures a signal propagation delay through a series of memory elements. In one embodiment the memory elements are configured in series so that together they form a delay circuit. In another embodiment the memory elements are configured in a loop to form a ring oscillator. Each memory element propagates a signal to a subsequent memory element so that the time the signal takes to traverse all of the memory elements is proportional to the average delay induced by the individual elements. This proportionality provides an effective means for measuring the delays of those components. Various embodiments of the invention measure the speeds at which memory elements can be preset, cleared, written to, read from, or clock enabled.
摘要:
Disclosed methods for utilizing programmable logic devices that contain at least one localized defect. Such devices are tested to determine their suitability for implementing selected customer designs that may not require the resources impacted by the defect. If the FPGA is found to be unsuitable for one design, additional designs may be tested. The test methods in some embodiments employ test circuits derived from a user design to verify PLD resources required for the design. The test circuits allow PLD vendors to verify the suitability of a PLD for a given customer design without requiring the vendor to understand the design.
摘要:
Fault coverage for the programmable interconnect of a programmable logic device (PLD) is provided. A user's design is modeled, thereby determining the programmable interconnect path in the device. The user's logic design is then modified, thereby facilitating the detection of faults. Specifically, any function generators in the PLD are implemented as predetermined logic gates, thereby forming a logic gate tree design. The synchronous elements in the user's design are preserved and transformed, if necessary, to provide controllability. Then, a vector can be exercised in the new design. A first readback of the PLD can be compared to a second readback of a fault-free model of the design.
摘要:
A circuit measures the signal propagation delay through a selected test circuit. The test circuit is provided with a feedback path so that the test circuit and feedback path together form a free-running oscillator. The oscillator then automatically provides its own test signal that includes alternating rising and falling signal transitions on the test-circuit input node. A phase discriminator samples the output of the oscillator and accumulates data representing the signal propagation delay of either rising or falling signal transitions propagating through the test circuit. The worst-case delay associated with the test circuit can then be expressed as the longer of the two. Knowing the precise worst-case delay allows IC A designers to minimize the guard band and consequently guarantee higher speed performance.