For low-complexity linear-phase FIR digital filters which have coefficients expressed as canonic signed digit (CSD) code, a design method to impose power-of-two DC gain is proposed. Output signal level can easily be compensated to that of input so that cascading many stages do not cause any gain errors, which are harmful in, for example, high precision measurement systems. The design is formulated as an optimization problem with magnitude response constraints. The integer linear programming modified for CSD codes is solved by the branch and bound method. The design example shows the effectiveness of the obtained filter in comparison with existing CSD filters. Also, an evaluation method for the area to implement the filter into field programmable gate array (FPGA) is proposed. The implementation example shows that the minimum critical path is obtained with only a little increase in the die area.

This paper presents a new performance and routability-driven routing algorithm for symmetrical array-based field-programmable gate arrays (FPGAs). The contribution of our work is to overcome one of the most critical limitations of the previous routing algorithms: inaccurate estimations of routing density which were too general for symmetrical FPGA. To this end, we devised new routing density measures that are directly linked to the structure (switch block) of symmetrical FPGA, and utilize them consistently in global and detailed routings. With the use of the proposed accurate routing metrics, we developed a new routing algorithm called a reliable net decomposition-based routing which is very fast, and yet produces excellent routing results in terms of net/path delays and routability. An extensive experiment was carried out to show the effectiveness of our algorithm based on the proposed cost metrics. In summary, when compared to the best known results in the literature (TRACER-fpga_PR and SEGA), our algorithm has shown 31.9% shorter longest path delay and 23.0% shorter longest net delay even with about 9 times faster execution time.

In this paper, we propose a method to minimize multiple-valued decision diagrams (MDDs) for multiple-output functions. We consider the following: (1) a heuristic for encoding the 2-valued inputs; and (2) a heuristic for ordering the multiple-valued input variables based on sampling, where each sample is a group of outputs. We first generate a 4-valued input 2-valued multiple-output function from the given 2-valued input 2-valued functions. Then, we construct an MDD for each sample and find a good variable ordering. Finally, we generate a variable ordering from the orderings of MDDs representing the samples, and minimize the entire MDDs. Experimental results show that the proposed method is much faster, and for many benchmark functions, it produces MDDs with fewer nodes than sifting. Especially, the proposed method generates much smaller MDDs in a short time for benchmark functions when several 2-valued input variables are grouped to form multiple-valued variables.

A delay-optimal technology mapping algorithm is developed on a general model of FPGA with hard-wired non-homogeneous logic block architectures which is composed of different sizes of look-up tables (LUTs) hard-wired together. This architecture has the advantages of short delay of hard-wired connections and area-efficiency of non-homogeneous structure. The Xilinx XC4000 is one commercial example, where two 4-LUTs are hard-wired to one 3-LUT. In this paper, we present a two-dimensional labeling approach and a level-2 node cut algorithm to handle the hard-wired feature. The experimental results show that our algorithm generates favorable results for Xilinx XC4000 CLBs. Over a set of MCNC benchmarks, our algorithm produces results with 17% fewer CLB depth than that of FlowMap in similar CPU time on average, and with 4% fewer CLB depth than that of PDDMAP on average while PDDMAP needs 15 times more CPU time.

In designing a field-programmable gate array (FPGA)-based processor for motion stereo, a parallel memory system and a simple interconnection network for parallel data transfer are essential for parallel image processing. This paper, firstly, presents an FPGA-oriented hierarchical memory system. To reduce the bandwidth requirement between an on-chip memory in an FPGA and external memories, we propose an efficient scheduling: Once pixels are transferred to the on-chip memory, operations associated with the data are consecutively performed. Secondly, a rectangular memory allocation is proposed which allocates pixels to be accessed in parallel onto different memory modules of the on-chip memory. Consequently, completely parallel access can be achieved. The memory allocation also minimizes the required capacity of the on-chip memory and thus is suitable for FPGA-based implementation. Finally, a functional unit allocation is proposed to minimize the complexity between memory modules and functional units. An experimental result shows that the performance of the processor becomes 96 times higher than that of a 400 MHz Pentium II.

In this paper, we present our work on the design of a new FPGA architecture targeted for high-performance bit-serial pipeline datapath. Bit-parallel systems require large amount of routing resource which is especially critical in using FPGAs. Their device utilization and operation frequency become low because of large routing penalty. Whereas bit-serial circuits are very efficient in routing, therefore are able to achieve a very high logic utilization. Our proposed FPGA architecture is designed taking into account the structure of bit-serial circuits to optimize the logic and routing architecture. Our FPGA guarantees near 100% logic utilization with a straightforward place and route tool due to high routability of bit-serial circuits and simple routing interconnect architecture. The FPGA chip core which we designed consists of around 200k transistors on 3.5 mm square substrate using 0.5 µm 2-metal CMOS process technology.

Synchronous Digital Hierarchy (SDH) and Synchronous Optical Network (SONET) are the standards for lightwave transmission systems, which can accommodate various existing signal types via Tributary Units (TUs) or Virtual Tributaries (VTs). In the SDH standards, Tributary Unit-11 (TU-11) is used to transport the DS1 signal with payload pointer and path overheads. In this paper, asynchronous floating mode TU-11 Mapper is designed by FPGAs for transmit and receive devices. The DS1 signal is mapped into TU-11 frame, and through Combus interface, then directly added/dropped into/from the VC-4 payload by taking advantage of the byte order frame format of SDH. In the add direction, a synchronizer with efficient stuffing algorithm is designed to minimize the waiting time jitter and absorb the frequency offset, the instantaneous jitter, the wander, and the gap of TU-11 data payload. In the drop direction, a desynchronizer implemented by a novel all digital phase locked loop and FIFO is used to accommodate the effect of irregular spacing of frame format and jitters generated by the pointer movement and bit justification. A prototype circuit board is built with the designed TU-11 Mapper and embedded in an STM-1 ADM system for long term testing.

For FA (factory automation) and ATE (automatic test equipment) in the industrial area, the standard bus is required to increase the system performance of multiprocessor environment. VME (versa module european package format) bus is appropriated to the standard bus but has the features that is the small of package and the low density of board. Beside, the density of board and semiconductor have grown to become a significant issues that affect the development time, project cost and field diagnostics. To fit this trend, in this paper, the author composed Revision C. 1 (IEEE Std. P1014-1987) of the integrated environment for the main function such as arbitration, interrupt and interface between VMEbus and several control modules. Also the designed VME system controller is implemented on FPGA that can be located even into Slot 1. The control and function modules are coded with VHDL mid-fixed description method and then those operations are verified by simulation. As a result of experiment, the author confirmed that the most important about the operation of Bus timer that Bus error signal should occur within 56 µs, and both control and function modules have the reciprocal operation correctly. Thus, the constructed VHDL library will be able to apply the system based VMEbus and ASIC design.

This paper describes a CORDIC-based direct digital frequency synthesizer in comparison with a ROM-based architecture. To optimize the hardware design parameters, we perform numerical analysis of the quantization effects for ROM and CORDIC-based architectures. The hardware costs of them are estimated in FPGA, which shows that the CORDIC-based architecture becomes better than the ROM-based when the required accuracy is 9 bits or more.

This paper presents a new design for testing SRAM-based field programmable gate arrays (FPGAs). The original FPGA's SRAM memory is modified so that the FPGA may have the facility to loop the testing configuration data inside the chip. The full testing of the FPGA is achieved by loading typically only one carefully chosen testing configuration data instead of the whole configurations data. The other required configurations data are obtained by shifting the first one inside the chip. As a result, the test becomes faster. This method does not need a large off-chip memory for the test. The evaluation results prove that this method is very effective when the complexity of the configurable blocks (CLBs) or the chip size increases.

The homogeneous structure of field programmable gate arrays (FPGAs) suggests that the defect tolerance can be achieved by shifting the configuration data inside the FPGA. This paper proposes a new approach for tolerating the defects in FPGA's configurable logic blocks (CLBs). The defects affecting the FPGA's interconnection resources can also be tolerated with a high probability. This method is suited for the makers, since the yield of the chip is considerably improved, specially for large sizes. On the other hand, defect-free chips can be used as either maximum size, ordinary array chips or fault tolerant chips. In the fault tolerant chips, the users will be able to achieve directly the fault tolerance by only shifting the design data automatically, without changing the physical design of the running application, without loading other configurations data from the off-chip FPGA, and without the intervention of the company. For tolerating defective resources, the use of spare CLBs is required. In this paper, two possibilities for distributing the spare resources (king-shifting and Horse-allocation) are introduced and compared.

Multimedia mobile communication systems are expected to be realized in the near future. In such systems, multipath fading can cause severe degradations of the quality of the communications due to its wide bandwidth, especially in urban areas. Adaptive array antennas can be attractive solution for overcoming the multipath fading. Suppression can be achieved with the adaptive array by cophasing and combining multipath signals in the space and time domain. On the other hand, the concept of software antenna has been proposed. The software antenna recognizes radiowave environments and appropriately reconfigures itself for the signal processing required by the recognized environment. Efficient implementations can be expected if these functions are realized by the software. In this paper, we propose two types of the adaptive array systems which is reconfigurable depending on the radiowave environment as a realization of the concept of the software antenna. They recognize the environment by using the eigenvalue decomposition of space domain correlation matrices and reconfigure their structures of the signal processing. The principle and performance are examined by theoretical means and through computer simulations.

The design of high performance-circuits using Field-Programmable Gate Arrays (FPGAs) requires a balance between the FPGA's architecture and CAD algorithms. Conventional FPGAs and CAD algorithms are developed independently, which makes it difficult to implement application circuits. To solve this problem, we developed a CAD-verified FPGA whose architecture was designed at the same time as the CAD algorithms. This paper shows how a CAD-verified FPGA architecture can simplify a routing algorithm. The algorithm is studied in terms of computational complexity and is simplified using the properties of our FPGA (switch module structure and the number of routing resources). The routing algorithm is almost one hundred times faster than that of the conventional router, and the quality of its circuits is also improved.

This paper presents a new approach to simulation of Dynamically Reconfigurable Logic (DRL) systems, which offers better accuracy of modelling dynamic reconfiguration than previously reported techniques. Our method, named Clock Morphing (CM), is based on modelling dynamic reconfiguration via a reconfigured module clock signal, while using a dedicated signal value to indicate dynamic reconfiguration. We discuss problems associated with the other approaches to DRL simulation and describe the main principles behind the proposed technique. We further demonstrate feasibility of a CM DRL simulation on its example implementation in VHDL.

This paper presents a new number representation called the Signed-Weight (SW) number system, which is useful for designing configurable counter-tree architectures for digital signal processing applications. The SW number system allows the unified manipulation of positive and negative numbers in arithmetic circuits by adjusting the signs assigned to individual digit positions. This makes possible the construction of highly regular arithmetic circuits without introducing irregular arithmetic operations, such as negation and sign extension in the two's complement representation. This paper also presents the design of a Field-Programmable Digital Filter (FPDF) architecture--a special-purpose FPGA architecture for high-speed FIR filtering--using the proposed SW arithmetic system.

An evolutionary algorithm is used to evolve a digital circuit which computes a simple hash function mapping a 16-bit address space into an 8-bit one. The target technology is FPGA, where the search space of the algorithm is made of the combinational functions computed by cells and of the interconnections among cells. The evolutionary technique has been applied to five different interconnection topologies, specified by neighbourhood graphs. This circuit is readily applicable to the design of set-associative cache memories. Possible use of the evolutionary approach presented in the paper for on-line tuning of the function during cache operation is also discussed.

The programming circuit of SRAM-based FPGAs consists of two shift registers, a control circuit and a configuration memory (SRAM) cell array. Because the configuration memory cell array can be easily tested by conventional test methods for RAMs, we focus on testing for the shift registers. We first derive test procedures for the shift registers, which can be done by using only the faculties of the programming circuit, without using additional hardware. Next, we show the validness of the test procedures. Finally, we show an application of the test procedures to test Xilinx XC4025.

A method for circular pattern recognition in a binary image and its implementation onto an FPGA are described. The proposed method is based on the template matching method using a modified matching degree. This method is implementable onto an FPGA and can realize a real-time system. The usefulness of the proposed method was confirmed by numerical simulations. The real-time performance was confirmed by experiments on the FPGA designed by using Verilog-HDL CAD tool.

The mapping from a global routing to a feasible detailed routing in a number of 2D array routing structures has been shown to be an NP-complete problem. These routing structures include the Xilinx style routing architecture, as well as architectures with significantly higher switching flexibility. In response to this complexity, a different class of FPGA routing structures called Greedy Routing Architectures (GRAs) have been proposed. On GRAs, optimally routing each switch box, in a specified order, leads to an optimal chip routing. Because routing each switch box takes polynomial time, the mapping problem on GRAs can be solved in polynomial time. In particular, an H-tree GRA with W2+2W switches per switch box (SpSB) and a 2D array GRA with 4W2+2W SpSB have been proposed. In this paper, we improve on these results by introducing an H-tree GRA with W2/2+2W SpSB and a 2D array GRA with 3.5W2+2W SpSB. These new GRAs have the same desirable mapping properties of the previously described GRAs, but use fewer switches.

In this paper, we will discuss circuit minimization techniques based on the multiple output capability of FPGA blocks. Since previous methods only consider two independent output functions, we will discuss a more complicated case when the two functions are mutually related. We also discuss a method to maximize flexibility of a specified cell output in the given FPGA block. If a set of possible functions for a cell which will not change the FPGA output function is large, we call that the flexibility of this cell is high. The concept of Sets of Pairs of Functions to be Distinguished (SPFDs) introduced by Yamashita et al. is a powerful tool to minimize a given FPGA circuits. In this paper, an extension of the concept, Priority based SPFDs (PSPFDs) is introduced to maximize the flexibility of output functions realized by such internal cells. By using PSPFDs for our new method, we can utilize the multiple output capability very well. Combination with the previous methods with PSPFDs is also shown to be important. We have implemented these methods and applied them to MCNC benchmarks mapped into 5-variable function blocks. To make a comparison with other methods, we have implemented methods using well-known merging algorithms utilizing the same multiple output capability. Experimental results show that our methods can reduce the number of blocks in the initial circuits by 40% on average. This reduction ratio is 16% higher than that of previous methods.