SIS is an interactive tool for synthesis and optimization of sequential circuits Given a state transition table, a signal transition graph, or a logic-level description of a sequential circuit, it produces an optimized net-list in the target technology while preserving the sequential input-output behavior Many different programs and algorithms have been integrated into SIS, allowing the user to choose among a variety of techniques at each stage of the process It is built on top of MISII [5] and includes all (combinational) optimization techniques therein as well as many enhancements SIS serves as both a framework within which various algorithms can be tested and compared, and as a tool for automatic synthesis and optimization of sequential circuits This paper provides an overview of SIS The first part contains descriptions of the input specification, STG (state transition graph) manipulation, new logic optimization and verification algorithms, ASTG (asynchronous signal transition graph) manipulation, and synthesis for PGA’s (programmable gate arrays) The second part contains a tutorial example illustrating the design process using SIS

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SIS : A System for Sequential Circuit Synthesis

From the Publisher:
This work covers all aspects of physical design. The book is a core reference for graduate students and CAD professionals. For students, concept and algorithms are presented in an intuitive manner. For CAD professionals, the material presents a balance of theory and practice. An extensive bibliography is provided which is useful for finding advanced material on a topic. At the end of each chapter, exercises are provided, which range in complexity from simple to research level.

Algorithms for VLSI Physical Design Automation

Field-Programmable Gate Arrays (FPGAs) have become one of the key digital circuit implementation media over the last decade. A crucial part of their creation lies in their architecture, which governs the nature of their programmable logic functionality and their programmable interconnect. FPGA architecture has a dramatic effect on the quality of the final device's speed performance, area efficiency, and power consumption. This survey reviews the historical development of programmable logic devices, the fundamental programming technologies that the programmability is built on, and then describes the basic understandings gleaned from research on architectures. We include a survey of the key elements of modern commercial FPGA architecture, and look toward future trends in the field.

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FPGA Architecture: Survey and Challenges

A programmable logic array integrated circuit has a number of programmable logic modules which are grouped together in a plurality of logic array blocks ("LABs"). The LABs are arranged on the circuit in a two dimensional array. A conductor network is provided for interconnecting any logic module with any other logic module. In addition, adjacent or nearby logic modules are connectable to one another for such special purposes as providing a carry chain between logic modules and/or for connecting two or more modules together to provide more complex logic functions without having to make use of the general interconnection network. Another network of so-called fast or universal conductors is provided for distributing widely used logic signals such as clock and clear signals throughout the circuit. Multiplexers can be used in various ways to reduce the number of programmable interconnections required between signal conductors.

Programmable logic array integrated circuits

A user-configurable circuit architecture includes a two dimensional array of functional circuit modules disposed within a semiconductor substrate. A first interconnect layer disposed above and insulated from the semiconductor substrate contains a plurality of conductors and is used for internal connections within the functional circuit modules. A second interconnect layer disposed above and insulated from the first interconnect layer contains a plurality of segmented tracks of conductors running in a first direction and is used to interconnect functional circuit module inputs and outputs. A third interconnect layer disposed above and insulated from the second interconnect layer contains a plurality of segmented tracks of conductors running in a second direction, some of the segments of conductors forming intersections with ones of the segments of the conductors in the second interconnect layer, and is used to interconnect functional circuit module inputs and outputs to implement the desired applications. A plurality of user-configurable interconnect elements are placed directly between the second and third interconnect layers at the intersections of selected segments of the segmented conductors in the second and third interconnect layers. More user-configurable interconnect elements are located between adjacent segments of the segmented conductors in both the second and third interconnect layers. Pass transistors located in the semiconductor substrate in between the functional circuit modules are connected between adjacent segments in both the second and third interconnect layers and between selected intersecting segments in the second and third interconnect layers.

Programmable interconnect architecture

An architecture for electrically configurable gate arrays using a two-terminal antifuse element is described. The architecture is extensible, and can provide a level of integration comparable to mask-programmable gate arrays. This is accomplished by using a conventional gate array organization with rows of logic modules separated by wiring channels. Each channel contains segmented wiring tracks. The overhead needed to program the antifuses is minimized by an addressing scheme that utilizes the wiring segments, pass transistors between adjacent segments, shared control lines, and serial addressing circuitry at the periphery of the array. This circuitry can also be used to test the device prior to programming and observe internal nodes after programming. By providing sufficient wiring tracks segmented into carefully chosen lengths and a logic module with a high degree of symmetry, fully automated placement and routing is facilitated. >

An architecture for electrically configurable gate arrays

A CMOS electrically configurable gate array that combines the flexibility, efficiency, extendability, and performance of mask-programmed gate arrays with the convenience of user programmability is described. The implementation is facilitated by a novel two-terminal antifuse programmable element and a configurable interconnect technology. The chip has been fabricated using 2- mu m n-well CMOS technology with two-layer metallization. >

A CMOS electrically configurable gate array

A novel architecture for CMOS electrically configurable gate arrays using a two-terminal antifuse element is described. The architecture is extensible and can provide a level of integration comparable to mask-programmable gate arrays. This is accomplished by using a conventional gate array organization with rows of logic modules separated by wiring channels. Each channel contains segmented wiring tracks. The overhead need to program the antifuses is minimized by an addressing scheme that utilizes the wiring segments, pass transistors between adjacent segments, shared control lines, and serial addressing circuitry at the periphery of the array. By providing sufficient wiring tracks segmented into carefully chosen lengths and a logic module with a high degree of symmetry, fully automated placement and routing is facilitated. >

The Act-2 family of CMOS field-programmable gate arrays (FPGAs) uses an electrically programmable antifuse and novel architectural and circuit features to obtain higher logic densities while increasing speed and routability. Improvements include: two new logic modules, novel I/O and clock driver circuitry, and more flexible and faster routing paths. New addressing circuitry shortens programming time and speeds complete testing for shorts, opens, and stuck-at faults. Fully automatic placement and complete routing are retrained. Special software tools used for architectural exploration and layout generation are discussed. >

A. El Gamal

Papers

An architecture for electrically configurable gate arrays

A CMOS electrically configurable gate array

An architecture for electrically configurable gate arrays

An FPGA family optimized for high densities and reduced routing delay