Electronic digital logic circuitry – Multifunctional or programmable – Array
Reexamination Certificate
1999-01-21
2001-01-30
Tokar, Michael (Department: 2819)
Electronic digital logic circuitry
Multifunctional or programmable
Array
C326S039000
Reexamination Certificate
active
06181163
ABSTRACT:
BACKGROUND
1. Field of the Invention
The invention is generally directed to integrated circuits, more specifically to on-chip memory provided for run-time use with on-chip logic circuits. The invention is yet more specifically directed to on-chip memory provided for run-time use within Programmable Logic Devices (PLD's), and even more specifically to a subclass of PLD's known as Field Programmable Gate Arrays (FPGA's).
2a. Cross Reference to Related Applications
The following copending U.S. patent applications are owned by the owner of the present application, and their disclosure are incorporated herein by reference:
(A) Ser. No. 08/948,306 filed Oct. 9, 1997 by Om P. Agrawal et al. and originally entitled, “VARIABLE GRAIN ARCHITECTURE FOR FPGA INTEGRATED CIRCUITS”;
(B) (A) Ser. No. 08/996,049 filed Dec. 22, 1997 by Om P. Agrawal et al and originally entitled, DUAL PORT SRAM MEMORY FOR RUN-TIME USE IN FPGA INTEGRATED CIRCUITS;
(C) Ser. No. 08/996,361 filed Dec. 22, 1997, by Om Agrawal et al. and originally entitled, “SYMMETRICAL, EXTENDED AND FAST DIRECT CONNECTIONS BETWEEN VARIABLE GRAIN BLOCKS IN FPGA INTEGRATED CIRCUITS”;
(D) Ser. No. 08/995,615 filed Dec. 22, 1997, by Om Agrawal et al. and originally entitled, “A PROGRAMMABLE INPUT/OUTPUT BLOCK (IOB) IN FPGA INTEGRATED CIRCUITS”;
(E) Ser. No. 08/995,614 filed Dec. 22, 1997, by Om Agrawal et al. and originally entitled, “INPUT/OUTPUT BLOCK (IOB) CONNECTIONS TO MAXL LINES, NOR LINES AND DENDRITES IN FPGA INTEGRATED CIRCUITS”;
(F) Ser. No. 08/995,612 filed Dec. 22, 1997, by Om Agrawal et al. and originally entitled, “FLEXIBLE DIRECT CONNECTIONS BETWEEN INPUT/OUTPUT BLOCKs (IOBs) AND VARIABLE GRAIN BLOCKs (VGBs) IN FPGA INTEGRATED CIRCUITS”;
(G) Ser. No. 08/997,221 filed Dec. 22, 1997, by Om Agrawal et al. and originally entitled, “PROGRAMMABLE CONTROL MULTIPLEXING FOR INPUT/OUTPUT BLOCKs (IOBs) IN FPGA INTEGRATED CIRCUITS”;
(H) Ser. No. 09/235,356 filed concurrently herewith, by inventors Bai Nguyen et al and entitled, MULTI-PORT SRAM CELL ARRAY HAVING PLURAL WRITE PATHS INCLUDING FOR WRITING THROUGH ADDRESSABLE PORT AND THROUGH SERIAL BOUNDARY SCAN;
(I) Ser. No. 09/008,762 filed Jan. 19, 1998 by inventors Om Agrawal et al and entitled, SYNTHESIS-FRIENDLY ARCHITECTURE WITH VARIABLE LENGTH AND VARIABLE TIMING INTERCONNECT; and
(J) Ser. No. 09/235,615 filed concurrently herewith by inventors inventors Om Agrawal et al and entitled, FPGA INTEGRATED CIRCUIT HAVING EMBEDDED SRAM MEMORY BLOCKS WITH REGISTERED ADDRESS AND DATA INPUT SECTIONS.
2c. Cross Reference to Related Patents
The disclosures of the following U.S. patents are incorporated herein by reference:
(A) U.S. Pat. No. 5,212,652 issued May 18, 1993 to Om Agrawal et al, (filed as Ser. No. 07/394,221 on Aug. 15, 1989) and entitled, PROGRAMMABLE GATE ARRAY WITH IMPROVED INTERCONNECT STRUCTURE;
(B) 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
(C) 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 Complex PLD's or CPLD's. This paradigm is characterized by devices such as the Advanced Micro Devices 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.).
Another evolutionary chain in the art of field programmable logic has branched out 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 device can be characterized as an integrated circuit that has four major features as follows.
(1) A user-accessible, configuration-defining memory means, such as SRAM, EPROM, EEPROM, anti-fused, fused, or other, is provided in the FPGA 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 an FPGA device can be formed of mixture of different kinds of memory elements if desired (e.g., SRAM and EEPROM).
(2) Input/Output Blocks (IOB's) are provided for interconnecting other internal circuit components of the FPGA device with external circuitry. The IOB's' may have fixed configurations or they may be configurable in accordance with user-provided configuration instructions stored in the configuration-defining memory means.
(3) Configurable Logic Blocks (CLB'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 CLB's of an FPGA has at least one lookup table (LUT) that is user-configurable to define any desired truth table,—to the extent allowed by the address space of the LUT. Each CLB may have other resources such as LUT input signal pre-processing resources and LUT output signal post-processing resources. Although the term ‘CLB’ was adopted by early pioneers of FPGA technology, it is not uncommon to see other names being given to the repeated portion of the FPGA that carries out user-programmed logic functions. The term, ‘LAB’ is used for example in U.S. Pat. No. 5,260,611 to refer to a repeated unit having a 4-input LUT.
(4) An interconnect network is provided for carrying signal traffic within the FPGA device between various CLB's and/or between various IOB's and/or between various IOB's and CLB's. At least part of the interconnect network is typically configurable so as to allow for programmably-defined routing of signals between various CLB's and/or IOB'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. A version of hard wired interconnect wherein a given conductor is dedicatedly connected to be always driven by a particular output driver, is sometimes referred to as ‘direct connect’.
In addition to the above-mentioned basic components, it is sometimes desirable to include on-chip reprogrammable memory that is embedded between CLB's and available for run-time use by the CLB's and/or resources of the FPGA for temporarily holding storage data. This embedded run-time memory is to be distinguished from the configuration memory because the latter configuration memory is generally not reprogrammed while the FPGA device is operating in a run-time mode. The embedded run-time memory may be used in speed-critical paths of the implemented design to implement, for example, FIFO or LIFO elements that buffer data words on a first-in/first-out or last-in/first-out basis. Read/write speed, data validating speed, and appropriate interconnecting of such on-chip embedded memory to other resources of the FPGA can limit the ability of a given FPGA architecture to implement certain speed-critical designs.
Modern FPGA's tend to be fairly
Agrawal Om P.
Chang Herman M.
Nguyen Bai
Sharpe-Geisler Bradley A.
Fliesler Dubb Meyer & Lovejoy LLP
Le Don Phu
Tokar Michael
Vantis Corporation
LandOfFree
FPGA integrated circuit having embedded SRAM memory blocks... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with FPGA integrated circuit having embedded SRAM memory blocks..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and FPGA integrated circuit having embedded SRAM memory blocks... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2532508