Scalable architecture for high density CPLDS having...

Details Scalable architecture for high density CPLDS having... Scalable architecture for high density CPLDS having...

1999-06-06

2001-02-06

Tokar, Michael (Department: 2819)

Electronic digital logic circuitry

Multifunctional or programmable

Array

C326S040000, C326S039000, C326S038000

Reexamination Certificate

active

06184713

ABSTRACT:

BACKGROUND
1. Field of Invention
The invention is generally directed to monolithic integrated circuits, and more specifically to a scalable architecture for use within Programmable Logic Devices (PLD's). It is even more specifically directed to a subclass of PLD's known as High-Density Complex Programmable Logic Devices (HCPLD's).
2. Cross Reference to Related Patents
The disclosures of the following U.S. patents are incorporated herein by reference:
(A) U.S. Pat. No. 5,764,078 issued Jun. 9, 1998 to Om Agrawal et al, and entitled, FAMILY OF MULTIPLE SEGMENTED PROGRAMMABLE LOGIC BLOCKS INTERCONNECTED BY A HIGH SPEED CENTRALIZED SWITCH MATRIX;
(B) U.S. Pat. No. 5,811,986 issued Sep. 22, 1998 to Om Agrawal et al, and entitled, FLEXIBLE SYNCHRONOUS/ASYNCHRONOUS CELL STRUCTURE FOR HIGH DENSITY PROGRAMMABLE LOGIC DEVICE;
(C) U.S. Pat. No. 5,818,254 issued Oct. 6, 1998 to Om Agrawal et al, and entitled, MULTI-TIERED HIERARCHICAL HIGH SPEED SWITCH MATRIX STRUCTURE FOR VERY HIGH DENSITY COMPLEX PROGRAMMABLE LOGIC DEVICES;
(D) U.S. Pat. No. 5,789,939 issued Aug. 4, 1998 to Om Agrawal et al, and entitled, METHOD FOR PROVIDING A PLURALITY OF HIERARCHICAL SIGNAL PATHS IN A VERY HIGH DENSITY PROGRAMMABLE LOGIC DEVICE;
(E) U.S. Pat. No. 5,621,650 issued Apr. 15, 1997 to Om Agrawal et al, and entitled, PROGRAMMABLE LOGIC DEVICE WITH INTERNAL TIME-CONSTANT MULTIPLEXING OF SIGNALS FROM EXTERNAL INTERCONNECT BUSES; and
(F) U.S. Pat. No. 5,185,706 issued Feb. 9, 1993 to Om Agrawal et al.
3. Description of Related Art
Field-Programmable Logic Devices (FPLD's) have continuously evolved to better serve the unique needs of different end-users. From the time of introduction of simple PLD's such as the Advanced Micro Devices 22V10™ Programmable Array Logic device (PAL), the art has branched out in several different directions.
One evolutionary branch of FPLD's has grown along a paradigm known as Field Programmable Gate Arrays or FPGA's. Examples of such devices include the XC2000™ and XC3000™ families of FPGA devices introduced by Xilinx, Inc. of San Jose, Calif. The architectures of these devices are exemplified in U.S. Pat. Nos. 4,642,487; 4,706,216; 4,713,557; and 4,758,985; each of which is originally assigned to Xilinx, Inc.
An FPGA may be generally characterized as a monolithic, integrated circuit that has an array of user-programmable, lookup tables (LUT's) that can each implement any Boolean function to the extent allowed by the address space of the LUT. User-programmable interconnect is typically provided for interconnecting primitive, LUT-implemented functions and for thereby defining more complex functions.
Because LUT-based function implementation tends to be functionally more exhaustive (broader) but speed-wise slower than gate-based (e.g., AND/OR-based) function implementation, FPGA's are generally recognized in the art as having a relatively expansive capability of implementing a wide variety of functions (broad functionality) but at relatively slow speed. Also, because length of signal routings through the programmable interconnect of an FPGA can vary significantly, FPGA's are generally recognized as providing relatively inconsistent signal delays whose values can vary substantially depending on how partitioning, placement and routing software configures the FPGA.
A second evolutionary chain in the art of field programmable logic has branched out along a paradigm known as Complex PLD's or CPLD's. This paradigm is characterized by devices such as the Vantis (subsidiary of Advanced Micro Devices Inc.) MACH™ family. Examples of CPLD circuitry are seen in U.S. Pat. No. 5,015,884 (issued May 14, 1991 to Om P. Agrawal et al.) and U.S. Pat. No. 5,151,623 (issued Sep. 29, 1992 to Om P. Agrawal et al.) as well as in other CPLD patents cited above.
A CPLD device can be characterized as a monolithic, integrated circuit (IC) that has four major features as follows.
(1) A user-accessible, configuration-defining memory means, such as EPROM, EEPROM, anti-fused, fused, SRAM, or other, is provided in the CPLD device so as to be at least once-programmable by device users for defining user-provided configuration instructions. Static Random Access Memory or SRAM is of course, a form of reprogrammable memory that can be differently programmed many times. Electrically Erasable and reProgrammable ROM or EEPROM is an example of nonvolatile reprogrammable memory. The configuration-defining memory of a CPLD device can be formed of a mixture of different kinds of memory elements if desired (e.g., SRAM and EEPROM). Typically it is of the nonvolatile, In-System reprogrammable (ISP) kind such as EEPROM.
(2) Input/Output means (IO's) are provided for interconnecting internal circuit components of the CPLD device with external circuitry. The IO's may have fixed configurations or they may include configurable features such as variable slew-output drivers whose characteristics may be fine tuned in accordance with user-provided configuration instructions stored in the configuration-defining memory means.
(3) Programmable Logic Blocks (PLB's) are provided for carrying out user-programmed logic functions as defined by user-provided configuration instructions stored in the configuration-defining memory means. Typically, each of the many PLB's of a CPLD has at least a Boolean sum-of-products generating circuit (e.g., and AND/OR array) or a Boolean product-of-sums generating circuit (e.g., and OR/AND array) that is user-configurable to define a desired Boolean function,—to the extent allowed by the number of product terms (PT's) or sum terms that are combinable by that circuit.
Each PLB may have other resources such as input signal pre-processing resources and output signal post-processing resources. The output signal post-processing resources may include result storing and/or timing adjustment resources such as clock-synchronized registers. Although the term ‘PLB’ was adopted by early pioneers of CPLD technology, it is not uncommon to see other names being given to the repeated portion of the CPLD that carries out user-programmed logic functions and timing adjustments to the resultant function signals.
(4) An interconnect network is generally provided for carrying signal traffic within the CPLD between various PLB's and/or between various IO's and/or between various IO's and PLB's. At least part of the interconnect network is typically configurable so as to allow for programmably-defined routing of signals between various PLB's and/or IO's in accordance with user-defined routing instructions stored in the configuration-defining memory means. Another part of the interconnect network may be hard wired or nonconfigurable such that it does not allow for programmed definition of the path to be taken by respective signals traveling along such hard wired interconnect.
In contrast to LUT-based FPGA's, gate-based CPLD's are generally recognized in the art as having a relatively less-expansive capability of implementing a wide variety of functions (in other words, not being able to implement all Boolean functions for a given input space) but being able to do so at relatively higher speeds. In other words, very wide functionality is sacrificed to obtain shorter, pin-to-pin signal delays. Also, because length of signal routings through the programmable interconnect of a CPLD is often arranged so it will not vary significantly despite different signal routings, CPLD's are generally recognized as being able to provide relatively consistent signal delays whose values do not vary substantially based on how partitioning, placement and routing software configures the CPLD. Many devices in the Vantis MACH™ family provide such a consistent signal delay characteristic under the Vantis trade name of SpeedLocking™. The more generic term, Speed-Consistency will be used interchangeably herein with the term, SpeedLocking™.
A newly evolving sub-branch of the growing families of CPLD devices is known as High-Density Comple

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