Abstract: A method and system are provided for increasing the accuracy of AC parametric testing. The invention provides a method of precisely estimating signal propagation delay time in an integrated circuit testing apparatus, wherein a plurality of signal propagation delay time measurements are taken and additional delay times are estimated by linearly interpolating the measured delays. A desired test point (desired output voltage at a given time) is established. Using a sample device, a slope is established on a time vs. voltage plot for a line through the desired test point. Where a desired test point falls between strobe times on a tester, linear extrapolation is used to calculate what voltages must be tested for at the two bracketing strobe times in order to guarantee the desired performance at the desired test point. One or more devices are then tested for the calculated voltages at the corresponding bracketing strobe times.

Abstract: The invention provides a Configurable Logic Element (CLE) preferably included in each of an array of identical tiles. A CLE according to the invention has four function generators. The outputs of two function generators are combined with a fifth independent input in a five-input-function multiplexer or function generator to produce an output that can be any function of five inputs, or some functions of up to nine inputs. The outputs of the other two function generators are similarly combined. The outputs of the two five-input-function multiplexers or function generators are then combined with a sixth independent input in a six-input-function multiplexer or function generator. The six-input-function multiplexer or function generator therefore produces an output that can be any function of up to six inputs. Some functions of up to nineteen inputs can also be generated in a single CLE.

Abstract: An input/output (I/O) circuit for transmitting output signals on or receiving input signals from an I/O terminal of an integrated circuit device, such as a Programmable Logic Device (PLD). The I/O circuit includes pull-up and pull-down transistors for generating output signals on the I/O terminal in an output mode, and an isolation transistor for limiting the voltage level transmitted to the pull-up transistor from the I/O terminal in an input mode. The isolation transistor is formed with a thicker gate oxide and a longer channel length than that of the pull-up and pull-down transistors, thereby allowing the isolation transistor to withstand voltages greater than Vcc of the PLD without damage. The isolation transistor is controlled using a charge pump provided on the PLD for programming non-volatile memory cells (e.g., EPROM, EEPROM or flash EPROM cells). The isolation transistor is produced during the same process steps used to produce high voltage transistors associated with the non-volatile memory cells.

Abstract: A hybrid HardWire device is provided that comprises a gate array core and a set of mask programmable I/O cells having I/O characteristics similar to those of an FPGA, i.e., sufficiently the same so the HardWire device can be used as a drop-in replacement for the FPGA with no redesign of the original system. Using this HardWire device, a user's design originally implemented in an FPGA can be emulated in the HardWire device, which then replaces the FPGA in the same board at a lower cost. In another embodiment, the I/O cells are mask programmable such that they can emulate the I/O characteristics of FPGAs from any of two or more FPGA families. This ability reduces the number of separate HardWire devices that must be designed, manufactured, tested, stored, and sold, and also simplifies the software required to convert designs to the new device. Some embodiments of the invention can also emulate other programmable devices such as PLDs.

Abstract: A method for designing an integrated circuit comprises the step of selecting a system-level parameterized module that performs a specified type of function. The method also includes the steps of specifying values for parameters of the selected system-level module and generating a netlist file from the selected system-level module. In one embodiment, the system-level parameterized module is selected from a family of system-level parameterized modules that each perform a particular function within different parameter ranges.

Abstract: A table-based computer user interface and a method of providing design parameters are provided for configuring circuits for programmable ICs. A design database describing a circuit is displayed in table-based format on a computer screen display. The design database may include a memory map including data to be placed in bit-storage space in the target programmable IC. This design database requires no schematics or HDL description of the circuit, even for application-specific circuits and other complicated circuits. The desired parameters are entered by the user, typically using toggle buttons, pull-down menus, or keyboard entry. The selected parameters and memory map data are then entered into the design database, thereby configuring the design database in accordance with the selected parameters. In one embodiment, the user interface can also be used to display read data from a previously programmed programmable IC.

Abstract: A method for implementing a large multiplexer with FPGA lookup tables. Logic that defines a multiplexer is detected and implemented according to the number of inputs and the target FPGA architecture. In one situation, a large multiplexer is implemented in two stages. The first stage implements wide AND functions of each of the input signals using lookup tables and carry logic. In a second stage, the resulting decoded input signals are combined in a wide OR gate again formed from lookup tables and a carry chain. In another situation, the multiplexer is implemented as a tree structure using lookup tables that implement 2:1 multiplexers in combination with other 2:1 multiplexers provided by configurable logic blocks of the FPGA.

Abstract: A decryption scheme is provided for encrypted configuration bitstreams in a programmable logic device. One embodiment includes circuitry for altering a decryption key for a plurality of encrypted bitstream portions, thereby providing a high level of security of the circuit layout embodied in the bitstream.

Abstract: A set of logic elements can be configured as a cascadable shift register. In one embodiment, a logic element for an FPGA can be configured as any one of a random access memory, a cascadable shift register and a lookup table. The data-in path to the shift register includes a cascade multiplexer for optionally forming large shift registers using multiple logic elements. Each logic element includes a plurality of memory cells which are interconnected such that the data output of each memory cell can serve as the input to the next memory cell, causing the logic element to function as a shift register. The cascade multiplexer allows the last bit of one logic element to be connected to the first bit of the next logic element, bypassing any decode logic of the lookup table. Variable tap shift registers of arbitrary length can be created by cascading lookup tables of plural logic elements in series.

Abstract: A semiconductor device tester and handler interface includes a tester and handler board. The board includes multiple test sites and has multiple layers of metallization traces. The handler side of the board includes a central area adapted to mount multiple semiconductor devices to be tested by a tester. The tester side of the board has tester contacts located to interface with a tester. Vias connect metallization traces in one metallization layer to metallization traces in another layer. The traces and vias are arranged to form paths from a tester contact to a test socket. The test sites are placed close to and sometimes superimposed on the tester contacts receiving the test signals. Thus delay is minimized and with multiple test sites, throughput is increased.

Abstract: An output driver circuit including a first path from an output pad to ground through a first switch, and a second path from the output pad to ground through series-connected second and third switches. The first switch is directly connected to a pull-down signal source, and one of the second and third switches is connected to the pull-down signal source through a one-shot circuit. In a pull-up state, the first and second switches are opened, and the one-shot circuit generates a stabilized output signal which closes the third switch. When the output driver circuit switches to a pull-down state, the first switch is closed, thereby connecting the output pad to ground via the first path. The signal change also closes the second switch. In addition, due to a propagation delay of the second signal through the one-shot circuit, the third switch initially remains closed, thereby also connecting the output pad to ground via the second path.

Abstract: A voltage regulator circuit in an integrated circuit (IC) device such as a Complex Programmable Logic Device (CPLD) includes a reference voltage generator, a tuning circuit, and an output driver circuit. The reference voltage generator converts an external supply voltage provided to the IC device into a stable reference voltage. The tuning circuit converts the stable reference voltage into a desired internal supply voltage, such as the reduced voltage required by deep sub-micron transistors. The output driver circuit provides the desired internal supply voltage with sufficient current to properly power the circuits of the IC device. The tuning circuit includes an op-amp and resistive elements configured in a voltage divider configuration in the negative feedback loop of the op-amp. The output of the op-amp can be set to the desired internal supply voltage by properly sizing the resistive elements.

Abstract: A circuit and method are provided for stress-testing EEPROMS by incrementally selecting and deselecting word lines. The circuit of the invention comprises a memory cell array, a set of decoders for decoding a memory address bus and controlling word lines for the memory cell array, a control circuit, and a shift register driven by the control circuit. Each bit of the shift register has the capability of overriding a group of one or more of the decoders. When the initiation signal is received by the control circuit, a state control bit is set high and is clocked through the shift register. The high bit overrides successive groups of decoders as it is shifted through the shift register, until all word lines in the memory cell array are selected. After the stress test has been performed, the state control bit is returned to zero and is cycled through the shift register on successive clock cycles, incrementally deselecting groups of word lines until all word lines are deselected.

Abstract: The invention provides an FPGA comprising an array of identical tiles. Each tile comprises a logic block that includes a Configurable Logic Element (CLE). In one embodiment, the CLE is implemented in two similar portions called "slices". Each slice has a separate carry chain. In a CLE with four function generators, each carry chain incorporates the outputs of two function generators.

Abstract: A field programmable gate array (FPGA) is provided that includes a plurality of pads and a plurality of delay locked loops (DLLs). Programmable connections enable any one of the DLLs to have multiple pads as inputs. Programmable connections also enable the DLLs to be selectively connected to one another. Programmable connections further enable the pads to be selectively connected to general interconnect circuitry or global clock drivers of the FPGA. Programmable connections are also provided for selectively connecting the DLLs to the global clock drivers. This FPGA structure enables the pads to be configured to receive either clock or non-clock signals. This structure also enables the FPGA to operate as a clock mirror, and to generate one clock signal from another clock signal on the FPGA.

Abstract: A programmable logic device (PLD) includes a plurality of logic resources, a plurality of multi-bit configuration memories (MBCMs), and a trigger logic structure. The plurality of MBCMs include multiple memory slices that allow the PLD to switch rapidly between configurations, or contexts. In one embodiment, at least one memory slice configures the PLD into a logic analysis context for providing on-chip testing. In one embodiment, the plurality of logic resources include a plurality of storage elements. State data generated by a user-defined context is stored in the plurality of storage elements. When the trigger logic structure provides a trigger signal, the PLD is reconfigured into the logic analysis context. The logic analysis context reads and processes the state data stored in the plurality of storage elements to test the performance of the user-defined context.

Abstract: A flash reconfigurable programmable logic device is applied as a dynamic execution unit for a sequence of instructions. The sequence of instructions includes control portion, and a portion which indicates which configuration of the flash configurable programmable logic device is to be used with that instruction. In each execution cycle, a configuration is selected in accordance with the instruction being executed, switching from one configuration of the programmable logic device to any other configuration stored on the device in a single cycle. The configuration store stores a set of configuration words defining respective logic functions of the configurable logic elements in the programmable logic device. The configuration select circuits operate to apply a selected configuration word from the set of configuration words to configure the configurable logic elements. An instruction store stores a sequence of instructions for execution by the programmable logic device.

Abstract: A radiation-tolerant logic circuit includes three similarly configured SRAM-based PLDs. These PLDs work in parallel to provide identical logic functions. To guard against data corruption that can result from radiation-induced upsets, the logic circuit includes a state-comparison circuit that periodically performs a bitwise comparison of the configuration and user data from each of the PLDs; if a bit from one PLD differs from the corresponding bit from the others, the state-comparison circuit sets a flag that indicates that the differing PLD is in error. The erroneous PLD is then reprogrammed using error-free state data. In one embodiment, the error-free state data is read from an error-free PLD.

Abstract: A RAM block includes a circuit for causing the RAM to provide all 0's on the output when a Reset signal is active. The Reset signal does not change the RAM contents but causes all outputs of the block RAM to be 0. This is useful when the RAM block is configured as a state machine. Thus, in an FPGA or other programmable device, an application can start the state machine in a known state with all address bits equal to 0 and can reset the state machine to this startup state. When the reset signal is active, the state machine feeds back the state of 0 to the address inputs of the RAM block that receive state feedback data, regardless of the data actually in those locations.

Abstract: A method and structure for testing static signal levels on an integrated circuit device using an electron beam deflection device. Each static signal is applied to a first terminal of a switch, such as an AND gate, an OR gate, or a pass transistor. An alternating control signal of approximately 1 MHz is transmitted to a second terminal of the switch such that the switch generates an output signal that is either constant (if the static signal is at a first level), or has a frequency equal to that of the alternating control signal (if the static signal is at a second level). The output signal is transmitted to a pad located on an exposed surface of the integrated circuit, where an electron beam deflection device is utilized to determine the static signal level by detecting the presence or absence of an alternating signal. A method for determining the voltage level of a signal includes applying the signal to the gate of a transistor and an alternating control signal to an input terminal.