Abstract: A computer-implemented method of optimizing a time multiplexed programmable logic device includes identifying a micro cycle, identifying all look-up tables (LUTs) from a list of LUTs of the PLD that may be scheduled in the micro cycle, ordering the LUTs in priority order, selecting the M LUTs with the highest priority (wherein M is the number of real LUTs in the PLD), labeling the M LUTs with the current micro cycle number, removing the M LUTs from the list, identifying the next micro cycle, and if labelled LUTs exist, then repeating all steps, otherwise exiting the computer-implemented method.

Abstract: An overridable data protection mechanism for unlocking/locking a PLD includes a data protect override key register, an input key register, and a comparator. After the user inputs an access code to the input key register, the software program sends an enabling signal to the comparator which in turn compares the bits stored in the data protect override key register and the bits in the input key register. If the bits in the two registers are identical, then the comparator outputs a disable data protect signal, thereby allowing the user to modify the configuration data in that PLD. After an incremented version control number and the new configuration data are downloaded to the PLD, the program sends a disabling signal to the comparator, thereby preventing further modification to the configuration data on that PLD.

Abstract: Non-volatile storage elements are provided on an integrated circuit, where the non-volatile storage elements are low voltage CMOS devices and hence compatible in a manufacturing sense with other similar transistors on an integrated circuit, thereby not requiring special types of transistors for the non-volatile storage. The non-volatile storage elements are either one-time programmable devices which are programmed by rupturing their gate oxide, EEPROM floating gate transistor cells, or other EEPROM cells.

Abstract: A memory cell array includes a first memory cell, a second memory cell, and a bit line which extends between the first and second memory cells. During normal operation, the bit line is used as a write path for data values to be written to the first and second memory cells. If the first memory cell is defective, the bit line is used to route the data value stored in the second memory cell to the first memory cell, effectively replacing the first memory cell with the second memory cell. In another embodiment, a memory cell array includes a first memory cell for storing a first data value and a second memory cell for storing a second data value. A first pair of bit lines are coupled to the first memory cell, and the first data value is written to the first memory cell on the first pair of bit lines. A second pair of bit lines are coupled to the second memory cell, and the second data value is written to the second memory cell on the second pair of bit lines.

Abstract: A selectively decoupled latch circuit used for latching a signal. The circuit contains an input line for accepting an input signal to the circuit. A latch is connected to the input line for latching the input signal. A transfer gate is also connected to the input line and latch for transferring the input signal to the latch according to a clock signal. A transistor is connected in a series with a feedback loop associated with the latch. The transistor selectively decouples the feedback path according to the clock signal. By selectively decoupling the feedback path, it is easier for a new input signal to become latched because contention between a prior latched signal versus the new input signal is minimized. An output line is connected to the latch for outputting a latched signal.

Abstract: A computer-implemented method of optimizing a time multiplexed programmable logic device includes identifying a micro cycle, identifying all look-up tables (LUTs) from a list of LUTs of the PLD that may be scheduled in the micro cycle, ordering the LUTs in priority order, selecting the M LUTs with the highest priority (wherein M is the number of real LUTs in the PLD), labeling the M LUTs with the current micro cycle number, removing the M LUTs from the list, identifying the next micro cycle, and if labelled LUTs exist, then repeating all steps, otherwise exiting the computer-implemented method.

Abstract: A carry logic circuit for a programmable logic device which uses a single function generator to create a carry propagate signal (P) and an output signal (S). The function generator includes a plurality of signal generation circuits, each of which is controlled by a first input signal (A) and a second input signal (B). One of the signal generation circuits is programmed to provide a desired carry propagate signal (P) in response to the first and second input signals (A,B). The carry propagate signal (P) is transmitted for use outside of the function generator to perform a carry propagation function for the carry logic circuit. The remaining signal generation circuits are programmed to generate one or more intermediate output signals in response to the first and second input signals (A,B). These intermediate output signals, in combination with carry propagate signal (P), are representative of the desired output signal (S).

Abstract: A method and apparatus for creating and utilizing a database of defective antifuses on a programmable logic device and comparing the list to a catalog of required connections in a design, wherein the process of comparing the two lists will determine whether the device, although flawed, is nonetheless compatible with the design to be implemented, thereby increasing device yield.

Abstract: A method and apparatus for converting a programmable logic device representation of a circuit into a second representation of the circuit. A circuit design is first captured and converted into a first representation of the circuit design. The first representation is for programming a programmable logic device. A first part of the first representation is for programming a configurable element in the programmable logic device. The first part of the first representation is used as a set of parameters for a general model of the configurable element. The second representation of the circuit includes the parameterized general model of the configurable element.

Abstract: A programmable logic device (PLD) including configurable circuitry for altering the speed-versus-power characteristics of the PLD after production, and for allowing the PLD to selectively operate on either a 3.3-volt or a 5-volt power supply. The configurable circuitry includes an input buffer, an output buffer and a reference generator. The input buffer includes a dedicated P-channel transistor connected in series with a dedicated N-channel transistor, and a plurality of trip-point adjustment transistors which are selectively connected in parallel with the dedicated transistors to adjust the trip-point of the input buffer by altering the N-to-P ratio. The output buffer includes two configurable buffers whose trip-points are also adjustable. A configurable reference generator is also provided for generating a high precision reference voltage which is supplied to the sense amplifiers located in the function blocks and interconnect matrix of the PLD.

Abstract: A method is described for measuring localized operating temperatures and voltages on an integrated circuit. The integrated circuit includes an oscillator circuit with a frequency that varies with temperature and/or applied voltage. The frequency of the oscillator is then determined, using a constant voltage, for a number of temperatures to establish a known relationship between oscillation frequency and temperature. Once the relationship is known, a similar oscillator is included within or adjacent a second circuit of the integrated circuit. The operating temperature or operating voltage of the second circuit may then be determined by monitoring the frequency of the oscillator while the second circuit is operational.

Abstract: A composable memory array for a programmable logic device includes a plurality of dedicated, serially coupled memory tiles. Each memory tile includes a plurality of dual-port memory cells, each having a first port and a second port, a plurality of first bit lines coupled to the first ports and a plurality of second data lines coupled to the second ports. The first and second bit lines extend across memory tiles. Each memory tile includes a plurality of first configuration circuits which allow the first bit lines of the memory tile to be coupled to the first bit lines of the previous memory tile. Thus, any number of consecutive memory tiles can be concatenated to form a memory array using the first set of bit lines. Non-consecutive memory tiles include a plurality of second configuration circuits which allow the second bit lines of the memory tile to be coupled to the second bit lines of a previous memory tile.

Abstract: A reference ring oscillator circuit (RROC) is used to determine timing characteristics of a test interconnect structure in an integrated circuit. The RROC includes an odd number of inverters coupled together in a ring manner and has defined test segments at which a test interconnect can be loaded. Reference timing characteristics of the unloaded RROC are determined according to a calibration method including the steps of: (a) directly measuring signal propagation delay through each segment of the RROC; (b) modeling each test segment using an RC tree type reference circuit model having reference elements; (c) simulating the reference circuit model to provide a functional relationship between two reference capacitors; (d) defining upper and lower bounds for propagation delay through the test segment in terms of the reference elements; (e) determining values for the reference capacitor elements; and (f) measuring a reference frequency of oscillation of the unloaded RROC.

Abstract: A method for placing a logic function into the function blocks of a complex programmable logic device (CPLD) to maintain the same input/output pin locations after the logic function is subsequently modified by a user. The method utilizes a weighting function to assign portions of the logic function to the function blocks such that sufficient resources are available in each function block to implement subsequent modifications to the logic function without changing the originally-assigned input and output pin locations. For each portion of the logic function, the weighting function is employed to identify the function block which implements the portion while maximizing the available resources in all of the function blocks. If a particular equation cannot be placed, the method utilizes a corrective measure such as fitting refinement, buffering and logic reformation to place the equation.

Abstract: A method and apparatus for loading memory within a reconfigurable programmable logic device including configuring the device as a RAM loader circuit, loading the RAM with data and then reconfiguring the device with a circuit utilizing the loaded RAM. The inventive method and apparatus allow use of the RAM as high density functional centers of the desired design immediately upon initialization of the circuit, without wasting valuable time or FPGA resources on a static, non-flexible RAM loader structure.

Abstract: An over-etched (OE) antifuse includes a lower electrode, an antifuse layer contacting the lower electrode by an over-etched via, and a second conductive layer formed on the antifuse layer. This over-etched via forms a trench in the lower electrode, wherein in one embodiment the depth of the trench approximates the thickness of the antifuse layer. The trench narrows the programming voltage distribution of the antifuses on the device, irrespective of topology. Because active circuits can be placed underneath the OE antifuses, the present invention dramatically reduces chip size in comparison to conventional devices.

Abstract: In an automated control system, a user must be authorized to modify the configuration data of a programmable logic device (PLD). After authorization is confirmed, the PLD is unlocked. Then, the configuration data of the PLD and the contents of a version control register are read back and archived, thereby providing a security back-up should the user need to retrieve the original data. After readback, the version control number is automatically incremented. This incremented version control number and the modified configuration data provided by the user are downloaded to the PLD. Finally, the PLD is locked.

Abstract: A programmable logic device (PLD) comprises at least one configurable element, and a plurality of programmable logic elements for configuring the configurable element(s). Alternatively, a PLD comprises an interconnect structure and a plurality of programmable logic elements for configuring the interconnect structure. In either embodiment, at least one of the programmable logic elements includes N memory cells. A predetermined one of the N memory cells forms part of a memory slice, wherein at least a portion of each slice of the programmable logic device is allocated to either configuration data or user data memory. Typically, one memory slice provides one configuration of the programmable logic device. In accordance with one embodiment, a memory access port is coupled between at least one of the N memory cells and either one configurable element or the interconnect, thereby facilitating loading of new configuration data into other memory slices during the one configuration.

Abstract: In accordance with the present invention, a programmable array includes hierarchical configuration and state storage. The array comprises an active storage for an active configuration and an active state as well as an inactive storage for one or more inactive configurations and one or more inactive states. The array further comprises logic and routing configured by the active configuration. The logic includes a plurality of combinational elements and a plurality of sequential logic elements for providing the states. Bits are transferred between the active and the inactive storage.

Abstract: A method of eliminating signal contention during reconfiguration of a programmable logic device includes the steps of: arranging a plurality of memory cells in sets and selectively programming the memory cells one set at a time, either in a first direction or a second direction. A structure for providing that selective programming includes a plurality of synchronous flip-flops, and a plurality of associated two-input multiplexers. A control signal in a first logic state provided to the multiplexers provides a first signal propagation direction through the flip-flops, whereas the control signal in a second logic state provides a second signal propagation direction through the flip-flops.