Abstract: An interface board and inserted modular IC interface cards allows variable length boundary scan chains. The chain can be constructed of any type of programmable integrated circuit (IC) in any order. The interface board contains a plurality of JTAG interfaces that respectively mate with standard adapter interfaces located on the modular IC interface cards. If less than the maximum number of modular IC interface cards are inserted into the interface board, a terminator card is inserted into the standard interface following the last modular IC interface card of the chain. The last test data output signal of the chain is routed back to a connector of the interface board. The interface board includes an output cascade connector that couples with an input cascade connector of another interface board so that any number of interface boards can be cascaded in series to expand the boundary scan chain.

Abstract: Structures and methods for selectively applying a well bias to only those portions of a PLD where such a bias is necessary or desirable, e.g., applying a positive well bias to transistors on critical paths within a user's design. A substrate for an integrated circuit includes a plurality of wells, each of which can be independently and programmably biased with the same or a different well bias voltage. In one embodiment, FPGA implementation software automatically determines the critical paths and generates a configuration bitstream that enables positive well biasing only for the transistors participating in the critical paths, or only for programmable logic elements (e.g., CLBs or lookup tables) containing those transistors. In another embodiment, negative well biasing is selectively applied to reduce leakage current.

Abstract: A system and method for translating a report file to a constraints file is provided. A circuit design is initially generated to be implemented on a logic device and a report file corresponding to the logic device is created. To transfer the circuit design to a different logic device, a constraints file generator analyzes the report file to determine characteristics of the logic device. A compatibility logic identifies a compatible device to the logic device based on the characteristics. A constraints file is then generated in accordance with the compatible logic device such that the circuit design can be re-targeted to the compatible device.

Abstract: A differential comparator having offset correction and common mode control providing stable op amp output that changes only due to the original inputs coming into the comparator. The difference comparator has increased common-mode difference tolerance, and large op-amp offset tolerance, as well as fast decision time.

Abstract: An electrical alignment test structure enables monitoring and measuring misalignment between layers (or associated masks) of an IC. The alignment test structure comprises a target region and an alignment feature in different layers. The target region and the alignment feature may be formed in diffusion and polysilicon layers, respectively or in well and diffusion layers, respectively. In both embodiments, the alignment feature controls the size of a conductive channel in the target region. Misalignment can be checked by comparing channel resistance with a baseline (no misalignment) resistance. In another embodiment, the target region and alignment feature are formed in the diffusion and polysilicon layers, respectively, wherein the alignment feature controls the relative widths of the source and drain regions. Misalignment can be checked by comparing current flow with a baseline current.

Abstract: A clock divider circuit that adds little additional delay on the clock path. Each rising and falling edge of an input clock signal triggers a pulse from a pulse generator circuit. These pulses are passed to a control circuit. True and complement versions of the input clock signal are provided to a multiplexer circuit. Under the direction of the control circuit, the multiplexer circuit passes selected rising edges of the true clock signal, and selected falling edges of the complement clock signal, to an output clock terminal of the clock divider circuit. When neither the true nor the complement clock signal is passed by the multiplexer, a keeper circuit retains the value already present at the output clock terminal.

Abstract: A memory cell comprises a multilayer gate heating structure formed over a channel region between source and drain regions. The multilayer gate heating structure comprises polysilicon and metal silicide layers stacked over a similarly shaped gate oxide. When a programming voltage is applied across the metal silicide layer, there is intense localized heating. The heating causes segregation of the channel dopant atoms towards the source and drain regions, lowering the threshold voltage of the device. The heating causes carrier activation in the polysilicon layer and dopant penetration through the oxide layer into the channel region, thereby increasing the threshold voltage of the device.

Abstract: A charge pump circuit that can be used in a phase-locked loop circuit provides a differential output signal that has a common mode voltage. The charge pump includes a common mode feedback circuit that maintains a predetermined common mode voltage on output connection of the charge pump. The charge pump can operate with a small supply voltage. In one embodiment, the charge pump can operate with a supply voltage that is less than 2.0 volts and maintain a common mode voltage that is less than 1.0 volts. The common mode feedback circuit includes current mirror circuitry and bias circuitry. The current mirror circuitry and the bias circuitry adjust the common mode voltage in response to input signals.

Abstract: Described are systems for producing differential logic signals and circuits for biasing the voltages of the differential logic signals. These systems can be adapted for use with different loads by programming one or more programmable elements. One embodiment includes a series of driver stages, the outputs of which are connected to one another. The driver stages turn on successively to provide increasingly powerful differential amplification. This progressive increase in amplification produces a corresponding progressive decrease in output resistance, which reduces the noise associated with signal reflection. The systems can be incorporated into programmable IOBs to enable PLDs to provide differential output signals.

Abstract: A method of designating circuit element positions using uniform coordinate systems that can be applied to non-uniform logic arrays. A “site map” is constructed comprising a uniform array of “sites”. A uniform coordinate system is applied to the site map. The various logic blocks, which may be of different types and sizes, are mapped to the site array. The result is the imposition of a uniform coordinate system on a non-uniform logic array, using the intervening abstraction of a site array. Because the site array is uniform, a relative location constraint applied to a site within the site array retains its validity regardless of the location of the site within the site array, even when the relative location constraints are normalized.

Abstract: A method of fabricating a pack tray is provided wherein a plurality of modules are secured in a master frame. Each pack tray typically includes two types of modules: a chip module having an aperture therein to secure an integrated circuit chip and a pick-up module for picking up the pack tray. In one embodiment, all modules are identical in size. In another embodiment, the modules differ in size.

Abstract: A power control output circuit for a PLD that allows the PLD to selectively operate in either a low current (“normal”) output mode, or a high current power control mode. In one embodiment, the power control output circuit is incorporated into a special Input/Output Blocks (PC-IOB) of the PLD. When no power control function is needed, a high current output portion of the power control output circuit is deactivated by storing an associated data value a power control configuration memory cell of the PLD, and an output driver of the PC-IOB generates low current output signals on a device I/O terminal. To perform power control functions, a portion of the PLD's programmable logic circuitry is configured to generate a power control data signal, and the high current output portion of the power control output circuit is enabled by storing a corresponding data value in the power control configuration memory cell.

Abstract: Method and apparatus for tolerating defects in a programmable logic device (PLD). A PLD includes a plurality of configurable logic elements and interconnect resources, wherein one or more of the configurable logic elements and interconnect resources have circuit defects. A design program is executed that is suitable for run-time reconfiguration of the PLD. The design program includes executable code that specifies a circuit design and generates a configuration bitstream that implements the circuit design on the programmable logic device. The design program also includes code that selectively skips the configurable logic elements and interconnect resources that contain the defects. In various embodiments, an individual configurable logic element, an entire row, or an entire column of elements can be skipped responsive to an input parameter.

Abstract: A fast, space-efficient lookup table (LUT) for programmable logic devices (PLDs) in which the write decoder, read decoder and memory block of the LUT are modified to improve performance while providing a highly efficient layout. Both the write decoder and the read decoder are controlled by LUT input signals, and data signals are transmitted directly to each memory circuit of the memory block (i.e., without passing through the write decoder). The read decoder includes a multiplexing circuit made up of a series of multiplexers that are directly controlled by the input signals received from the interconnect resources of the PLD. In one embodiment, a configurable logic block is provided with a single write decoder that is shared by a first LUT and a second LUT.

Abstract: An FPGA architecture and method enables partial reconfiguration of selected configurable logic blocks (CLBs) connected to an address line without affecting other CLBs connected to the same address line. Partial reconfiguration at a memory cell resolution is achieved by manipulating the input voltages applied to the address and data lines of an FPGA so that certain memory cells are programmed while other memory cells are not programmed. In addition, partial reconfiguration at a CLB resolution can be achieved by hardwiring the FPGA to enable selection of individual CLBs for reconfiguration.

Abstract: Method and apparatus for doubling the throughput rate of data transmission on a logic path comprising providing two latches that alternately receive successive bits of the data stream to be transmitted and a multiplexer having data transmission paths that are alternately clocked by two separate clocks, which clocks are substantially 180 degrees out of phase.

Abstract: Method and circuits to create reduced field programmable gate arrays (RFPGA) from the configuration data of field programmable gate arrays (FPGA) are disclosed. The configurable elements of the FPGA are replaced with standard cell circuits that reproduce the functionality of the configured FPGA. Specifically, reduced logic blocks are derived from the configuration data of configurable logic blocks. Similarly, reduced input/output blocks and reduced matrices are derived from the configuration data for input/output blocks and programmable switch matrices of the FPGA, respectively. The reduced logic blocks are arranged in a similar layout to the original CLBs so that timing relationships remain similar in the RFPGA and FPGA. The actual timing of the RFPGA can be modified by increasing or decreasing the timing delay on various signal paths based on the FPGA design or additional timing constraints.

Abstract: A programmable logic device (PLD) can be reconfigured without losing state data derived from logical operations performed using a previous logic configuration. One PLD in accordance with the invention includes a number of configurable logic blocks (CLBS) and input/output blocks (IOBs). Each CLB and IOB includes a number of configuration memory cells adapted to store the logical function of the FPGA. Each CLB and IOB additionally includes user storage elements adapted to store state data that results from the PLD performing a programmed logical function, such as a selected combinatorial function of input signals. The PLD preserves the data stored in the user storage element as the PLD is reconfigured. The state data is therefore available for use by the PLD after the PLD is reconfigured to perform a new logic function.

Abstract: A programmable logic device (PLD) includes a die having first and second bond pads, each being weakly pulled to a first voltage. A package enclosing the die has an external pad configured to receive a second voltage. A conductor couples one and only one of the first and second bond pads to the external pad, such that one bond pad is pulled to the first voltage, and the other bond pad is pulled to the second voltage. A logic circuit on the die is coupled the first and second bond pads. The logic circuit enables the PLD to be configured in response to a first type of bit stream if the first bond pad is pulled to the second voltage, and enables the PLD to be configured only in response to a second type of bit stream if the second bond pad is pulled to the second voltage. In another embodiment, a bond pad is weakly pulled to a first voltage, and can be connected or not connected to an external pin for applying a second voltage.

Abstract: An apparatus and method for enabling hot swapping of programmable logic devices (PLDs) and boards containing PLDs is provided. If the hot swap capability is desired, a hot swap terminal on the PLD is set to facilitate a floating state on the input/output pad of the PLD. Further, the input buffer and the output buffer of the PLD are disabled. In one embodiment, a predetermined voltage is provided on the output terminal of the input buffer. In this configuration, the hot swap circuit eliminates any leakage current, ensures no static current occurs, and provides appropriate signals to the internal circuits of the PLD.