In combination with a wheel for a bicycle and the like having an annular rim, a hub rotatable about its axis, and axially offset groups of circumferentially spaced spokes which centrally support the hub on the rim; a wheel decorating ornament comprising an annular, planar sheet of material decorated on opposite sides, axially disposed between the groups of spokes and radially disposed between the rim and the hub.

The Test Access Port and Boundary Scan Architecture

A computer’s memory system is the repository for all the information the computer’s central processing unit (CPU, or processor) uses and produces. A perfect memory system is one that can supply immediately any datum that the CPU requests. This ideal memory is not practically implementable, however, as the three factors of memory capacity, speed, and cost are directly in opposition. By placing smaller faster memories in front of larger, slower, and cheaper memories, the performance of the memory system may approach that of a perfect memory system—at a reasonable cost. The memory hierarchies of modern general-purpose computers generally contain registers at the top, followed by one or more levels of cache memory, main memory (all three are semiconductor memory), and virtual memory (on a magnetic or optical disk). Figure 1 shows a memory hierarchy typical of today’s (1995) commodity systems. Performance of a memory system is measured in terms of latency and bandwidth. The latency of a memory request is how long it takes the memory system to produce the result of the request. The bandwidth of a memory system is the rate at which the memory system can accept requests and produce results. The memory hierarchy improves average latency by quickly returning results that are found in the higher levels of the hierarchy. The memory hierarchy usually reduces bandwidth requirements by intercepting a fraction of the memory requests at higher levels of the hierarchy. Some machines, such as high-performance vector machines, may have fewer levels in the hierarchy—increasing cost for better predictability and performance. Some of these machines contain no caches at all, relying on large arrays of main memory banks to supply very high bandwidth. Pipelined accesses of operands reduce the performance impact of long latencies in these machines. Cache memories are a general solution to improving the performance of a memory system. Although caches are smaller than typical main memory sizes, they ideally contain the most frequently accessed portions of main memory. By keeping the most heavily used data near the CPU, caches can service a large fraction of the requests without needing to access main memory (the fraction serviced is called the hit rate). Caches require locality of reference to work well transparently—they assume that accessed memory words will be accessed again quickly (temporal locality) and that memory words adjacent to an accessed word will be accessed soon after the access in question (spatial locality). When the CPU issues a request for a datum not in the cache (a cache miss), the cache loads that datum and some number of adjacent data (a cache block) into itself from main memory. To reduce cache misses, some caches are associative—a cache may place a given block in one of several places, collectively called a set. This set is content-addressable; a block may be accessed based on an address tag, one of which is coupled with each block. When a new block is brought into a set and the set is full, the cache’s replacement policy dictates which of the old blocks should be removed from the cache to make room for the new. Most caches use an approximation of least recently used

Memory systems

This paper introduces a new hybrid ASIC/FPGA chip architecture that is being developed in collaboration between IBM and Xilinx, and highlights some of the design challenges this offers for designers and CAD developers. We review recent data from both the ASIC and FPGA industries, including technology features, and trends in usage and costs. This background data indicates that there are advantages to using standard ASICs and FPGAs for many applications, but technical and financial considerations are increasingly driving the need for a hybrid ASIC/FPGA architecture at specific volume tiers and technology nodes. As we describe the hybrid chip architecture ,we point out evolving tool and methodology issues that will need to be addressed to enable customers to effectively design hybrid ASIC/FPGAs. The discussion highlights specific automation issues in the areas of logic partitioning, logic simulation, verification, timing, layout and test.

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A hybrid ASIC and FPGA architecture

We take a fresh look at the problems posed by deep submicron (DSM) geometries and re-open the investigation into how DSM effects are most likely to affect future design methodologies. We describe a comprehensive approach to accurately characterize the device and interconnect characteristics of present and future process generations. This approach results in the generation of a representative strawman technology that is used in conjunction with analytical model simulation tools and empirical design data to obtain a realistic picture of the future of circuit design. We then proceed to quantify the precise impact of interconnect, including delay degradation due to noise, on high performance ASIC designs. Having determined the role of interconnect in performance, we then reconsider the impact of future processes on ASIC design methodology.

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Getting to the bottom of deep submicron

Electrical current source circuitry for a bus is described. The circuitry includes transistor circuitry coupled between the bus and ground for controlling bus current, control circuitry coupled to the transistor circuitry, and a controller coupled to the control circuitry for controlling the transistor circuitry. The controller comprises a variable level circuit comprising setting circuitry for setting a desired current for the bus and transistor reference circuitry coupled to the setting circuitry. The variable level circuit provides a first voltage. Voltage reference circuitry provides a reference voltage. Comparison circuitry is coupled to the voltage reference circuitry and to the variable level circuit for comparing the first voltage with the reference voltage. Logic circuitry is responsive to a trigger signal from the comparison circuitry. An output of the logic circuitry is coupled to the control circuitry in order to turn on the transistor circuitry in a manner dependent upon an output of the logic circuitry.

Electrical current source circuitry for a bus

Power is gated from global terrain to a voltage island while controlling leakage and managing transient power supply noise. The voltage island includes a field effect transistor (FET) power gate, a first connection to a global voltage source and a second connection to a disable signal source, and an island voltage net for supplying voltage to devices on the island. A power gate control circuit is responsive to the disable signal source for generating a test signal for selectively turning off the FET power gate as the disable signal source goes to a logical ‘1’, and for turning on the FET power gate as said disable source goes to a logical ‘0’. The FET power gate is responsive to the disable signal source being off for connecting the island voltage net to the global voltage source. A turn on finisher circuit is responsive to the disable signal transitioning to on and to the test signal for holding the power gate solidly on; and a turn off finisher circuit is responsive to the disable signal transitioning to off and to the test signal for holding said power gate solidly off.

System and method for power gating

An ASIC book comprising a gate-array format of ESD components is provided. A customized, optimized and tuned ESD network can be constructed from the ASIC book. Novel ESD circuitry having inter-rail ESD circuitry and single-rail ESD circuitry can be constructed. The inter-rail ESD circuitry is scaleable and comprises one or more diode strings for interconnecting a pair of power rails. The ESD trigger voltage for a diode string is set by the number of diodes within the customized diode string and preferably a sufficient number of diodes are provided within each diode string for power-up and power-down sequence independence. The single-rail ESD circuitry is connected to a level-shifter and may comprise an RC discriminator comprising a customizable plurality of NFET transistors connected in series. The RC discriminator may be connected to a clamping transistor via a buffering circuit, such as an inverter stage, that isolates the gate capacitance of the clamping transistor from the RC discriminator. In a second aspect of the invention an ASIC book comprising a gate-array format of ESD components is provided. A customized, optimized and tuned ESD network can be constructed from the ASIC book.

ASIC book to provide ESD protection on an integrated circuit

A voltage divider device includes a double gate field effect transistor (FET) having a first gate and a second gate disposed at opposite sides of a body region. An input voltage is coupled between the first and second gates, and an output voltage is taken from at least one of a source of the FET and a drain of the FET, wherein the output voltage represents a divided voltage with respect to the input voltage.

Structure and method for implementing oxide leakage based voltage divider network for integrated circuit devices

An integrated circuit comprising: a parent terrain (element 12); and a hierarchal order of nested voltage islands within the parent terrain (element 12), each higher-order voltage island nested (Figure 5, element 32) within a lower-order voltage island (Figure 5), each nested voltage island (Figure 5, element 32) having the same hierarchal structure.

Nested voltage island architecture

A method and apparatus for designing very large scale integrated circuit devices, most particularly level sensitive scan design (LSSD) devices, by inclusion of a plurality of distributed delay lines originating at input terminals of the device, and controlling the inhibiting and enabling of driver circuits connected to the output terminals of the device, as required to regulate operation of device drivers during a plurality of testing operations.

Douglas W. Stout

Papers

System and method for power gating

ASIC book to provide ESD protection on an integrated circuit

Structure and method for implementing oxide leakage based voltage divider network for integrated circuit devices

Nested voltage island architecture

Integrated circuit driver inhibit control test method