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 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: 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 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: 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: 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.

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: 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 one-shot system for loading a bitline shift register with a typical test pattern is described. Each bitline latch within the bitline shift register is augmented with a one-shot circuit that may pull-up or pull-down the value stored in the bitline latch. The choice of a particular memory test pattern dictates the control of the one-shot circuit.

Abstract: Memory cell structures and related circuitry for use in non-volatile memory devices are described. The cell structures can be fabricated utilizing standard CMOS processes, e.g. sub 0.35 micron or sub 0.25 micron processes. Preferably, the cell structures can be fabricated using 0.18 micron or 0.15 micron standard CMOS processes. Advantageously, the cell structures can be programmed so that a conductive path is formed between like type materials. For example, in certain cell structures a cell is programmed by applying a programming voltage in such a way as to form a conductive path between a p-type gate and a p-type source/drain region or an n-type gate and an n-type source/drain region. Programming cells in this manner advantageously provides a programmed cell having a low, linear resistance after programming. In addition, novel charge pump circuits are provided that, in a preferred embodiment, are located “on chip” with an array of memory cells.

Abstract: A method and apparatus for developing run-time parameterizable logic cores for programmable logic devices (PLDs). In various embodiments, logic cores are defined in a run-time reconfiguration program, the logic cores having output pins and input pins. A pre-route tool routes selected ones of the output pins to selected ones of the input pins and generates program code for the run-time reconfiguration program. The program code generated by the pre-route tool programs interconnect resources that make the required connections. The automatically generated program code is then parameterized and included in the run-time reconfiguration program.

Abstract: An FPGA includes a configuration control circuit having an internal memory that stores default configuration data which may configure the some or all of FPGA's logic blocks into a default state. A compressed bitstream includes one or more frame control bits indicative of whether corresponding configuration data is included in the bitstream. During configuration of the FPGA, the compressed bitstream is provided to the configuration control circuit from the external memory. As each frame control bit is received, its logic state is determined. If the frame control bit indicates that corresponding configuration data is included in the bitstream, the corresponding configuration data is read from the bitstream into a frame register. If, on the other hand, the frame control bit indicates that corresponding configuration data is not in the bitstream, default configuration data is read from the internal memory into the frame register.

Abstract: Described are systems and methods for measuring the size uniformity of circuit features defined by the critical dimension of an integrated-circuit fabrication process. An integrated circuit is configured to include a number of oscillators, each occupying a region of the integrated circuit. Each oscillator oscillates at a frequency that depends on the critical dimension of features in the region in which it is formed. Consequently, the critical dimensions of regions across the surface of the integrated circuit can be mapped and compared by comparing the oscillation frequencies of identical oscillators formed in various regions of the integrated circuit. In programmable logic devices, oscillators can be implemented using programmable logic resources. In other embodiments, small, simple oscillators can be placed at various locations on the integrated circuit.

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 user data is therefore available for use by the PLD after the PLD is reconfigured to perform a new logic function.

Abstract: A configuration memory architecture for an FPGA eliminates the need for a regular array of word lines and bit lines. The memory includes memory bytes, each of which has eight SRAM latches, a single flip-flop and a one-of-eight decoder having 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 flip-flops of all memory bytes for a logic block are coupled together in a serpentine shift register. Loading of configuration data involves shutting down all paths through the decoder, shifting all configuration bits for the “0” position SRAM latch of each memory byte into the shift register, and setting the address bits to the decoder so as to create a conductive path on each memory byte from the output of the flip-flop to the data input of the 0 latch. The process is then repeated for the seven other SRAM latch positions.

Abstract: An FPGA has an on-chip processor that reads configuration data onto the FPGA and controls the loading of that configuration data into FPGA configuration memory cells. After FPGA power-up, the processor reads a configuration mode code from predetermined terminals of the FPGA. If the configuration mode code has a first value, then the processor executes a first configuration program so that configuration data is received onto the FPGA in accordance with a first configuration mode. If the configuration mode code has a second value, then the processor executes a second configuration program so that configuration data is received onto the FPGA in accordance with a second configuration mode. The configuration programs can be stored in metal-mask ROM on-chip so they can be changed without re-laying out the remainder of the FPGA. Providing multiple configuration programs allows the FPGA to support multiple configuration modes using the same processor hardware.

Abstract: An anti-aliasing filter with adaptable cutoff frequency. In various embodiments, the filter includes a calibrator/adaptor section and an anti-aliasing filter section. Both sections include a cascaded arrangement of adjustable delay circuits, and the calibrator/adaptor section includes a control circuit. A reference signal is input to the delay circuits and the control circuit of the calibrator/adaptor section, and an analog input signal is input to the delay circuits of the anti-aliasing filter. The control circuit compares the directly received reference signal to the reference signal from the last delay circuit and generate an adjustment signal responsive to the comparison. The delay intervals of all the delay circuits are adjustable responsive to the adjustment signal from the control circuit.

Abstract: An FPGA architecture and method to reduce the size of the bitstream used in configuring or reconfiguring the FPGA. To facilitate features of the compression process, an FPGA is modified to implement an addressable data register in place of a conventional shift register. This allows data frames to be arranged in order of similarity, and a bitstream formed from one full data frame along with an address into which the frame is to be loaded, and subsequent partial data frames including only changed words along with the row address of the changes and the column address into which modified frames are to be loaded, rather than shifting in entire frames of data for subsequent frames.

Abstract: A method is disclosed for communicating with an FPGA interface device having a microcontroller when the on-board microcontroller is not responsive to commands from a host system. If the host system determines that the microcontroller is not responsive to commands, the host system sends a null character to the interface device at a predetermined baud rate which is significantly distinguishable from baud rates normally used for communicating with the microcontroller. A logic circuit on the interface device monitors the baud rate of incoming data, and if a null character at the predetermined baud rate is detected, the logic circuit toggles the reset pin of the microcontroller. In response thereto, the microcontroller re-boots itself, and is thereafter able to communicate with the host system. Additional commands are provided to the interface device by using other baud rates which are significantly distinguishable from the baud rates normally used.

Abstract: A system and method for configuring routing resources of a programmable logic device are presented in various embodiments. In one embodiment, a first function is provided that automatically generates configuration bits for configuration of routing resources to connect a source to a sink. The input parameters to the to the first function include the source and the sink. A second function is provided to automatically generate configuration bits for configuration of routing resources that connect a source to a plurality of sinks. The second function is responsive to input parameters specifying the source and plurality of sinks. Additional program interfaces are provided and each provides various controls over the routing process.