Abstract: 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.

Abstract: A floating gate memory device that includes a column latch circuit that is isolated from a series of bitlines by PMOS pass transistors controlled by a bitline latch switch circuit. The bitline latch switch circuit selectively applies either +5 V or −2 V signals to the gate terminals of the PMOS pass transistors, thereby allowing the PMOS pass transistors to selectively pass 0 (zero) Volts during, for example, program operations. A −2 V charge pump is activated to generate the −2 V signal during operations requiring 0 Volt bitline voltages, and is turned off during all other operations.

Abstract: A voltage translator features an isolation circuit, connected to two inverters which are operated by different voltage levels, to selectively isolate one of the inverters from the source voltage associated therewith. The voltage translator also includes a first inverter, a second inverter and a pull-up circuit. The first inverter is coupled between a first source voltage and ground, and has a signal input and an output node. The second inverter is coupled between a second source voltage and ground. The second inverter has an input node, connected to the output node, and a signal output. The pull-up circuit is connected between the input node and the signal output.

Abstract: 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. These signal transitions are counted over a predetermined time period to establish the period of the oscillator. The period of the oscillator is then related to the average signal propagation delay through the test circuit. The invention can be applied to synchronous components that might fail to oscillate by connecting the asynchronous set or clear terminal to the output terminal so that the oscillator oscillates at a frequency determined by the clock-to-out delay of those components.

Abstract: A method and system for programming the hardware of field programmable gate arrays and related reconfigurable resources as if they were software by creating hardware objects that implement application level functionalities, operating system functionalities, and hardware functionalities. Further controlling and executing the hardware objects via high level software constructs and managing the reconfigurable resources, such that the reconfigurable resources are optimized for the tasks currently executing.

Abstract: A mask programmable IC is provided that includes dedicated boundary scan logic in the I/O cells. Valuable core logic resources therefore need not be consumed to implement boundary scan logic. In one embodiment, one boundary scan cell is provided per I/O cell. Another embodiment provides great flexibility in emulating any of several FPGAs in any of several packages. In this embodiment, two boundary scan cells are provided for each I/O pad, each cell alone being capable of providing the boundary scan functions associated with one I/O pad. By selectively choosing which of the boundary scan cells are included in the boundary scan data chain, the order of the boundary scan chain of the emulated FPGA in any of two or more packages can be reproduced. Boundary scan behavior is therefore emulated as well as the programmable logic behavior of the FPGA. In one embodiment, additional programmable interconnect lines traversing each boundary scan cell are provided.

Abstract: A clock signal is driven at one point onto a clock bus of an integrated circuit by a driver circuit. Oscillators are coupled along the length of the clock bus. The oscillators are all loosely coupled to one another through the clock bus such that all the oscillators oscillate together at the frequency of the clock signal. The oscillators add energy to the clock signal on the clock bus locally so that all the energy required to sustain the clock signal does not have to come from the point of origin. By reducing current flow down the clock bus across the series resistance of the clock bus, limits on propagation speed due to the series resistance of the clock bus are avoided. In one embodiment, less than 15 milliwatts is consumed to “propagate” a 1.36 gigahertz clock signal a distance of two centimeters down a clock bus of an integrated circuit at a propagation speed of approximately 2.1×107 meters per second.

Abstract: A configuration memory architecture for an FPGA that eliminates the need for a regular array of word lines and bit lines is disclosed. The memory is comprised, in the preferred embodiment, of a plurality of memory bytes. Each memory byte has eight SRAM latches, a single flip flop and a one-of-eight decoder having a data input coupled to the inverting output of the flip flop and eight individual data outputs, each of which is coupled to a data input of one of the SRAM latches. The decoder also has address and write control inputs which are coupled to a state machine or other programmable device that controls the sequencing of the loading operation to load configuration data into the memory. The flip flops of all the memory bytes are coupled together in a serpentine shift register.

Abstract: A method and apparatus for analyzing performance and density of a source design module for a target programmable gate array. The source design module is converted to logic for a selected target programmable gate array. Performance and density of the converted logic are then estimated. If the estimated performance level does not achieve a target performance level, then problematic design elements are automatically or optionally converted to functionally equivalent programmable gate array design elements. The performance and density of the target programmable gate array is again estimated using the new design elements. In another mode of operation, design guidance is provided in converting the problematic design elements.

Abstract: The invention provides a structure and method of generating a clock enable signal in a programmable logic device (PLD). A first embodiment of the invention comprises a clock enable circuit implemented such that the critical paths have only two levels of logic. In this embodiment, the critical paths are implemented in dedicated logic while other portions of the clock enable circuit are implemented using programmable logic. According to another embodiment of the invention, the clock enable circuit is located near the center of a first edge of the device. A first plurality of output registers are located along the first edge on either side of the clock enable circuit, with additional output registers being located along the two adjacent half-edges. Programmable interconnection points (PIPs) permit a clock enable interconnect line along the first edge to be programmably extended to the additional output registers. In another embodiment, the clock enable circuit is duplicated in two opposite edges of the device.

Abstract: 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.

Abstract: A programmable input/output structure comprised of three input circuits and one output circuit coupled to the pin of an FPGA with the input circuits and output circuits being selectively enabled by programming bits so that input signals may be accepted from TTL, GTL, GTLP, LVPECL or LVDS type external circuits. The programming bits can also selectively enable an output driver to simultaneously drive the same pin of the FPGA as an output with signals which are either TTL or GTL or GTLP compatible. Further, the slew rate of the output driver is programmable between slow, medium or fast.

Abstract: A method and system for converting an architecture-specific design of a first type into an architecture-specific design of a second type such that race conditions and other anomalies are detected in the second type. By identifying routing delays in a first architecture and what those same routing delays would be in a second architecture, the method and system verify that a design has been properly converted. The method and system are applicable to the conversion of programmable interconnect logic devices to mask programmable logic devices. For example, a method for verifying timing for a design implemented in a new device when the design is to be moved from an old device. The method is particularly useful for verifying timing in a mask programmable device (HardWire) when the design is being converted from a field programmable device (FPGA).

Abstract: Architecture for a programmable logic device is described which can operate at substantially faster clock rates than present programmable logic devices. Instead of employing passive circuit elements to interconnect the programmable logic elements and the input and output data buses, controllable active driver circuits are employed. These circuits eliminate essentially all of the resistance present in prior art passive connections.

Abstract: The invention provides parametric modules called Self Implementing Modules (SIMs) for use in programmable logic devices such as FPGAs. The invention further provides tools and methods for generating and using SIMs. SIMs implement themselves at the time the design is elaborated, targeting a specified FPGA according to specified parameters that may, for example, include the required timing, data width, number of taps for a FIR filter, and so forth. In one embodiment, the SIM parameters may be symbolic expressions, which may comprise strings or string expressions, logical (Boolean) expressions, or a combination of these data types. The variables in these expressions are either parameters of the SIM or parameters of the “parent” of the SIM. Parametric expressions are parsed and evaluated at the time the SIM is elaborated; i.e., at run-time, usually when the design is mapped, placed, and routed in a specific FPGA.

Abstract: A system and method for configuration of a programmable logic device using routing cores. A program executing on a processor includes instructions that select functions to be provided by the programmable logic device. The instructions invoke functions from a library of logic and router core generators to define logic cores and router cores to intercouple the logic cores. From the logic and router core definitions, the program utilizes a bit-stream library to generate programming bits. The programmable logic device is then loaded with the programming bits by the program.

Abstract: An interactive graphical software tool is provided that can be used to report the configuration data (i.e., the state of the various configuration bits) in a programmed device as well as to probe and stimulate circuits in the programmed device. A graphical or textual representation of the configuration data can be displayed. When used with a programmable device having addressable flip-flops, such as a member of the Xilinx XC6200 family, one embodiment of the invention can change the state of any addressable flip-flop in the configured device. The graphical tool of the invention is preferably implemented using a high level programming language such as Java and features a graphical point and click user interface, remote access to hardware, and symbolic debug capability.

Abstract: A method of communicating encrypted configuration data between a programmable logic device (PLD) and a storage device is included in one part of the invention. The method includes the following steps. Transmit encrypted configuration data stored in a storage device to the PLD. Decrypt the encrypted configuration data to generate a copy of the configuration data in the PLD. Configure the PLD using the copy of the configuration data. In one embodiment, the PLD transmits a key to the storage device. In another embodiment the key is separately entered into the storage device and the PLD and never transmitted between the PLD and the storage device. In another embodiment, the key is entered only into the PLD. The key is used to encrypt the configuration data.

Abstract: A plurality of flash electrically erasable programmable read only memory (EEPROM) cells is disclosed wherein metal lines couple both the sources and the drains of the flash cells. Reading of these flash cells is accomplished by applying a positive voltage to the source and reading from the associated metal source line. A soft erase scheme for increasing the threshold voltage of over-programmed flash cells is provided that prevents the leakage caused by applying a positive voltage to the drain.

Abstract: A logic/memory circuit (LMC) utilized in a configurable logic block (CLB) of a programmable logic device (PLD) that implements an eight-input lookup table (LUT) using an array of programmable elements arranged in rows and columns. A decoder is used to read bit values from one column (e.g., sixteen programmable elements) of the array. In one embodiment, a separate read bit line is provided to facilitate faster read operations. A sixteen-to-one multiplexer/demultiplexer circuit is used to pass selected bit values to an output terminal. The array of programmable elements is programmable both from configuration lines during a configuration mode, and by data transmitted on the interconnect resources through the multiplexer/demultiplexer circuit. In one embodiment, the programmable elements of the array are connected in pairs to product term generation circuitry, and input signals to the array are routed onto bit lines that are also connected to the product term generation circuitry.