Abstract: In an FPGA having a hierarchical routing structure, additional routing lines are provided which have different destinations for different cells within a block. A pattern is chosen which allows signal lines to turn corners conveniently. In one embodiment having cells arranged into 4.times.4 blocks, cells on the diagonal of a block generate signals which are provided to switches which form one boundary of the block.

Abstract: A data-cascading hierarchically arranged electrically configurable logic device (ECD) system and an enable-cascading hierarchically arranged ECD system are provided. In both cases, the configuration bitstream includes a local count and at least one remainder count for each ECD. The local count determines the amount of configuration data to be stored locally. By setting this count to zero, an ECD can be bypassed. The remainder count determines the amount of data to be stored by devices down one hierarchical branch from the local ECD. By setting this count to zero, this branch can be bypassed and ECDs of a second branch can be configured sooner. In the data cascading system, the counts determine how data is routed through the ECDs. In the enable cascading system, the data is broadcast to all ECDs. The counts determine when and if the configuration enable inputs of downstream ECDs are to be activated.

Abstract: A pipeline frame full detection circuit. The present invention is operable within a system that loads configuration data into an integrated circuit (IC) using a serial data stream and transfer mechanism. Configuration data is transferred into the IC in sequential frames of a specified size for a given IC. The first bit of the configuration data contains a frame full indicator. The configuration data is transferred into a shift register circuit and the last bit position(s) of the shift register circuit, in addition to being stored in the shift register circuit, are shifted along a special frame full pipeline to a control unit. The control unit, upon detecting the frame full indicator, asserts a parallel write command that causes the data of the shift register circuit to be parallel transferred to a receiving column of memory. New configuration data can then be serially shifted into the same shift register circuit after a reset signal.

Abstract: A method and system for measuring programmed antifuse resistance in an FPGA without disturbing the antifuse resistance. The method includes estimating a plurality of subparts of the programming path connecting low and high programming voltage sources on the FPGA device, measuring the path as a whole, and subtracting the sum total of the subparts from the whole path measurement, thereby deriving the antifuse resistance. If the derived antifuse resistance is higher than desired, programming and measurement may be repeated to ensure device longevity and accurate timing for implemented designs.

Abstract: A method in accordance with the present invention includes programming a plurality of semiconductor devices simultaneously, thereby dramatically increasing the number of devices programmed within a predetermined time. In one embodiment, this method includes arranging a first plurality of semiconductor devices into an array configuration. The first array is then programmed while a second plurality of semiconductor devices is arranged into the array configuration. The second array is then programmed, while the first array is unloaded and a third plurality of semiconductor devices is arranged into the array configuration. The present invention further includes the step of moving the first plurality of semiconductor devices in the array configuration to a programming position and the step of transferring the first plurality of semiconductor devices to an unloading position.

Abstract: A system and method for entering a circuit design into a computer using a schematic capture package. The schematic capture package is modified to include a library of state flow components represented by symbols which can be connected to produce a desired representation of the circuit design. The system allows a circuit design to be displayed on a video terminal using both state flow diagram and the schematic diagram symbols, with terminals of the state flow symbols connecting to terminals of the schematic symbols. The state flow diagram using state flow symbols is combined with a schematic diagram including schematic symbols to generate a netlist representing the combined circuit.

Abstract: An ESD protection circuit combines a split bipolar transistor with a transistor layout which exhibits very high tolerance to ESD events. The split bipolar transistor divides current among many segments and prevents the current hogging which often causes an ESD failure. Several splitting structures are disclosed, each combining a resistor in series with each segment to distribute current evenly. The transistor takes advantage of the snap-back effect to increase current carrying capacity. Layout positions metal contacts away from regions of highest energy dissipation. Layout also allows high currents to be dissipated through ESD protection structures and not through circuit devices such as output drivers or through parasitic bipolar transistors not designed for high current. Sharp changes in electron density are avoided by the use of high-diffusing phosphorus in N-regions implanted to both lightly and heavily doped levels. Critical corners are rounded rather than sharp.

Abstract: A programmable logic device (PLD) includes test circuitry compatible with the JTAG standard (IEEE Standard 1149.1). The PLD also includes a programmable JTAG-disable bit that can be selectively programmed to disable the JTAG circuitry, leaving the PLD to operate as a conventional, non-JTAG-compatible PLD. The PLD also includes means for testing the JTAG test circuitry to determine whether the JTAG circuitry is defective, and means for programming the JTAG-disable bit to disable the JTAG circuitry if the testing means determines that the JTAG circuitry is defective.

Abstract: An FPGA architecture offers logic elements with direct connection to neighboring logic elements and indirect connection through a routing matrix. A logic element and a portion of the routing matrix are formed as part of a tile, and tiles are joined to form arrays of selectable size. The routing matrix includes routing lines which connect just from one tile to the next and routing lines which extend longer distances through several tiles or through the entire chip. This combination is achieved by the formation of individual tiles, all of which are identical.

Abstract: According to the invention, a structure is provided for driving a bus line that is both fast and small. Instead of a plurality of tristate buffers, one for each input signal, a plurality of multiplexers is connected into a chain. The tristate enable line of the tristate buffer becomes the control line for enabling the multiplexer to place its own input signal into the chain instead of propagating the signal already in the chain. A buffer element then drives the resulting signal onto an output line of the chain. One embodiment of the invention includes lookahead logic similar to a lookahead carry chain. This allows large numbers of input lines to be connected to a bus line while retaining high speed. An embodiment implements the lookahead feature using AND gates and OR gates and thereby further increases speed and reduces size.

Abstract: A fast carry-out scheme in a field programmable logic array. The configurable logic blocks (CLBs) are arranged in columns. The carry-out signals are routed from the bottom CLB of a column to the top CLB of that column. The carry-out from the top-most CLB is then multiplexed onto a clock line that is normally used to conduct clocking signals to the CLBs. Instead of conducting clocking signals, the existing clock line is now used to route the carry-out signal onto a vertical longline spanning the entire height of the column. Eventually, the carry-out signal is routed from the longline to its destination CLB of the adjacent column via local interconnect resources.

Abstract: A circuit and method for testing Field Programmable Gate Arrays (FPGAs) comprises a programmable multiplexer for sequentially connecting columns of logic cells to enable the configuring of logic cell columns into one or more scan chains. Each column of logic cells contains an edge cell comprising a multi-input multiplexer, one of the multiplexer inputs being dedicated to receiving a signal from an adjacent cell, other of the inputs being connected to gate array input pads. A programmable control signal on the multiplexer enables the column to either receive test data from one of the gate array input pads or to connect as part of a scan chain by receiving a wrapping signal from the output logic cell of an adjacent column.

Abstract: A data line for an integrated circuit such as field programmable gate array, has a relatively fast rise time, consumes relatively low amount of current, and maintains a relatively fast fall time. A data conductor is connected to a circuit element providing a current path from the data conductor to a source of the supply voltage. A plurality of data-in drivers are connected to the data conductor which act in one state to pull the data conductor from the supply voltage to ground, and act in another state to present high impedance to the data conductor. A dynamic element is included, which connects an additional current path between the data line and the supply during transitions from ground to the supply, and which disconnects the additional current path otherwise. This speeds up the transitions from low to high, while not opposing the transitions from high to low.

Abstract: A method and structure for verifying interconnect structure of an FPGA device after programming. In a preferred embodiment, after programming, a single wire segment on each net of a layout is pulled down to a low reference voltage. Voltage levels on all wire segments of the device are then captured and shifted out of the device for comparison to the expected values. Low voltage levels on segments expected to remain high reveal short circuit flaws. High voltage levels on segments expected to remain low reveal open circuit flaws. The test is conducted simultaneously on a group of packed nets, wherein each group comprises a number of disjoint nets separated from one another by at least two MicroVia.TM. interconnects. A preferred packing method minimizes the number of net groups on a device for maximum test efficiency.

Abstract: A system for providing real time design feedback to a user of a data processing system for designing an electronic circuit includes a display system, a graphical, textual or mixed user input process which displays user input on the display system for designing an electronic circuit, and an implementation process with which generates an implementation of the electronic circuit in for example a field programmable gate array. Feedback is provided by monitoring the user input process to detect a change in the design of the electronic circuit. Upon detection of a change, information about the change is forwarded to the implementation process. The implementation process is executed as a background process to the user input process, in response to the change to produce implementation data on an incremental basis. Information about the implementation data is displayed on the display system as feedback to the user during the design process.

Abstract: A macrocell for a programmable logic device includes private product term assignments to provide various functions including set and reset, output enable, clocking, and inversion. Each of these additional functions is provided by assigning one of the product terms associated with the macrocell to perform one of these functions locally. By means of additional logic circuitry these functions are achieved either singly or in combination for a particular macrocell, thus improving macrocell flexibility and in some cases conserving pins of the chip of which the programmable logic array is a part.

Abstract: An field programmable gate array (FPGA) of cells arranged in rows and columns is interconnected by a hierarchical routing structure. Switches separate the cells into blocks and into blocks of blocks with routing lines interconnecting the switches to form the hierarchy. Also, select units for allowing memory bits to be addressed both individually and in large and arbitrary groups are disclosed. Further a control store for configuring the FPGA is addressed as an SRAM and can be dynamically reconfigured during operation.

Abstract: An integrated programmable logic device (PLD) includes flash EPROM storage transistors. The PLD includes a multiplexor that selectively provides program, erase, or verify voltages to the storage transistors. The program, erase, and verify voltages may be supplied using external power supplies or may be generated internally by on-chip charge-pump generators. A configurable memory on the PLD is used to adjust the output voltages from each of the on-chip charge-pump generators.

Abstract: Logic is represented in a schematic capture program as a generic symbol. The generic symbol represents a single underlying logic circuit, thereby decreasing library space. The generic symbol includes a configuration memory which is represented on the symbol by a plurality of pins. The generic symbol is configured by indicating the logic signals placed on the plurality of pins. In this manner, the generic symbol significantly increases the design choices available to the end user. Moreover, the generic symbol allows access to the underlying logic of the circuit via the selected bit pattern, thereby advantageously permitting the end user to perform functional simulation within the schematic environment. In one embodiment, a plug symbol is provided to schematically connect to the generic symbol. This plug symbol represents a predetermined pattern of bits, thereby significantly simplifying configuring the logic in the schematic capture program.

Abstract: A device independent, frequency driven layout system and method for field programmable gate arrays ("FPGA") which allow for a circuit designer to specify the desired operating frequencies of clock signals in a given design to the automatic layout system to generate, if possible, a physical FPGA layout which will allow the targeted FPGA device to operate at the specified frequencies. Actual net, path and skew requirements are automatically generated and fed to the place and route tools. The system and method of the present invention evaluates the frequency constraints, determines what delay ranges are acceptable for each electrical connection and targets those ranges throughout the layout.