Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
1999-09-30
2001-07-31
Smith, Matthew (Department: 2768)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C716S030000
Reexamination Certificate
active
06269467
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to integrated circuit (“IC”) device design, and more specifically to the design of systems re-using pre-designed circuit blocks.
BACKGROUND OF THE INVENTION
In recent years, constant innovation in silicon process technology has drastically reduced the price and increased the performance and functionality of integrated circuit devices, thus stimulating the development of the electronics manufacturing and information processing industries. In turn, these fast growing industries impose increasing demands on the integrated circuit design system developers for still faster and cheaper devices. As a result, the design industry is now undergoing drastic changes, including:
(1) Chip designs are getting larger and more complex. For example, in 1997, a typical integrated circuit contained from 100-500K gates. In 1998, the typical device contained one to two million gates. Technology in 1999 has shown the continuation of this trend with devices of four to six million gates being built.
(2) Chip designs are becoming more application-specific. In the early days of IC design, device manufactures would produce various “off-the-shelf” chips, which end users would design into their electronic products. Currently, electronic product manufactures more often order custom chip designs to perform specific functions.
(3) Electronic product development is now primarily driven by consumer demand, which has shortened product life cycles and, therefore shortened allowed design time and resources. For example, in 1997, the average design cycle was between 12-18 months. In 1998, that average time decreased to 10-12 months and in 1999 the industry is pushing towards 8-10 month design-cycle times.
(4) Design time constraints require parallel design effort. Formerly, critical design decisions for upstream system components could wait until downstream system component designs were verified. Design managers no longer have the luxury of sequentially performing design tasks. Several system components may have to be developed concurrently. Thus, design managers are required to make crucial predictions before at least some system component designs are complete.
To address these demands, electronic system design is now moving to a methodology known in the art as Block Based Design (“BBD”), in which a system is designed by integrating a plurality of existing component design blocks (also referred to in the art as “intellectual property blocks” or “IP blocks”). These pre-designed blocks may be obtained from internal design teams or licensed from other design companies, and may be supported by fundamentally different design structures and environments. Moreover, pre-designed blocks may be developed to meet different design requirements and constraints.
Another challenge faced by designers using BBD is the front-end (project acceptance) delays and risk brought about by uncertainty in determining system design feasibility. Current ASIC (application-specific integrated circuit) designs are primarily presented at the RTL (register transfer level) stage, and some even earlier, at specification level, to designers by customers. These designs are then partitioned in a manner based upon the limitations of available synthesis technology, according to the area, performance, and power tradeoffs required to provide cost-effective implementation. In this manner, the designer accepts a system specification as input and ultimately provides a netlist-level design for physical implementation (including design place, route, and verification). If design specifications are within the capabilities of the intended or available processing technology, including clocking, power, and size specifications, the available design methodology is reasonably predictable and works well with available circuit design tools.
However, the RTL-level design and the system-level design activities are typically uncoupled or loosely coupled, meaning there is no coherent link from the system-level functional definition to the ASIC (RTL) level. The RTL-level design is developed based upon a paper ASIC specification and verified by a newly formed test suit created around the ASIC interface. Thus, available design and implementation methodologies for ASIC design present a number of problems, which hamper efficient block integration.
First, current methodologies do not provide a top-down approach to comprehensively evaluate and ensure compatibility to integrate a plurality of design blocks provided by multiple sources having differing design considerations, while providing hierarchical verification and short assembly time within tight time-to-market constraints.
Also, existing methodologies for ASIC design do not provide scalability. A significant number of existing methodologies are focused around a flat design. This approach has led to significant problems in the length of time required to assemble the top-level design for a system having more than one million gates.
In addition, existing ASIC design methodologies are not suitable for reuse of pre-designed circuit blocks. Available schemes do not provide guidelines to solve the timing, clock, bus, power, block arrangement, verification, and testing problems associated with integrating circuit design blocks within specific device architectures. Thus, without a comprehensive approach to block reuse, existing methodologies bring about an ad-hoc and unpredictable design approach, reduce design realization feasibility, increase cost and time to delivery, and often trigger performance-reducing modifications to the pre-designed circuit blocks themselves in order to fit them into the designed system. Furthermore, existing methodologies do not provide performance trade-off analysis and feedback of critical design parameters, such as clock frequency, and area versus risk of successfully and predictably completing chip designs and implementations.
There is, therefore, a need for a methodology that can satisfy the evolving environment and address the shortcomings of the available art.
There is also a need for a suitable methodology for using and re-using pre-designed circuit blocks from multiple sources in a circuit design.
Combining IP blocks also brings about the need for “glue” logic, the logic that allows the blocks to work together on a single device. Glue logic is the logic primarily responsible for interconnecting design blocks, and normally resides between the blocks, dispersed throughout the design. Glue logic elements can be added to a design during various stages of chip planning, or can reside at the outermost boundary of each block within a design to act as an interconnect mechanism for the host block. Regardless of its source, glue logic must be optimally placed within the design to minimize wire congestion and timing complications which arise from placement of glue logic between blocks, introducing delays which may not have been contemplated by the original block designer.
There is therefore a need in the art to which the present invention pertains for an improved method of placing and distributing glue logic in a block based design.
There is also a need for a glue logic distribution mechanism that takes into account the functional affinity of various glue logic elements, and groups them into new design blocks.
There is also a need in the relevant art for a glue logic distribution mechanism that returns an optimized amount of glue logic to existing design
In addition, existing ASIC design methodologies are not suitable for reuse of pre-designed circuit blocks. Available schemes do not provide guidelines to solve the timing, clock, bus, power, block arrangement, verification, and testing problems associated with integrating circuit design blocks within specific device architectures. Since the circuit blocks are from multiple inconsistent sources, the challenge is how to integrate these circuit blocks into a circuit system in a fashion suitable to block-based design.
Therefore, there is a need for a method and apparatus suitable to inter-connect the
Chang Henry
Cooke Larry
Hunt Merrill
Ke Wuudiann
Lennard Christopher K.
Cadence Design Systems Inc.
Crosby, Heafey Roach & May
Garbowski Leigh Marie
Smith Matthew
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