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: 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 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 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 programmable shift register in which the length (e.g., number of bits), number and location of taps, operating mode (i.e., counting up/down) and number of skip states are configured by programming selected memory cells. The programmable shift register includes a plurality of flip-flops, a programmable interconnect circuit, a next-state control circuit and a mode control circuit. The output terminal of each flip-flop drives a different bus line in the programmable interconnect circuit. Each bus line is programmably connected to a plurality of I/O lines via programmable interconnect points (PIPs). At least two of the second lines are connected to the input terminal of each flip-flop via portions (e.g., multiplexers) of the mode control circuit. Programming the PIPs to link selected flip-flop input and output terminals forms one or more shift registers of a selected length.

Abstract: A scan lookahead skip structure that allows a programmable number of test bits, I/O blocks, flip-flops, or columns to be skipped. One embodiment of the structure includes multiplexers to skip the scan paths for several adjacent I/O blocks, flip-flops, or columns, thereby reducing the number of clock cycles and overall delay required to utilize the scan path.

Abstract: A memory system and method which allows a plurality of memory circuits to be operated independently as separate memories, or jointly as a single memory. Alternatively, the selected memory circuits are operated jointly and other memory circuits are operated independently. The configuration of the memory system can be varied dynamically during operation of the memory system.

Abstract: A set of module generators produce optimized implementations of particular circuit logic arithmetic functions for Field Programmable Gate Arrays (FPGAs) or other digital circuits. The module generators allow a circuit designer to spend more time actually designing and less time determining device-specific implementation details. The module generators accept a high level block diagram schematic of the circuit and automatically perform the detailed circuit design, including propagation of data types (precision and type) through the circuit, and low level circuit design optimization using a library of arithmetic and logic functions. The module generators are particularly useful for designs using field programmable gate arrays because of their unique architectures and ability to implement complex functions.

Abstract: A computer aided design system for electronic digital circuitry allows the circuit designer to design a circuit using high level block components, The designer specifies data type and precision (bus width) parameters as desired for whichever circuit blocks and/or busses he desires, Then the system propagates the data types and precision throughout the design automatically to achieve circuit-wide consistency, The system can also be used to verify a circuit design for data type and bus width consistency, The system can also be used to determine the mode of operation for the circuit blocks in the circuit.