Steven Trimberger

A time-multiplexed FPGA

This paper describes the architecture of a time-multiplexed FPGA. Eight configurations of the FPGA are stored in on-chip memory. This inactive on-chip memory is distributed around the chip, and accessible so that the entire configuration of the FPGA can be changed in a single cycle of the memory. The entire configuration of the FPGA can be loaded from this on-chip memory in 30 ns. Inactive memory is accessible as block RAM for applications. The FPGA is based on the Xilinx XC4000E FPGA, and includes extensions for dealing with state saving and forwarding and for increased routing demand due to time-multiplexing the hardware.

A 90nm low-power FPGA for battery-powered applications

Programmable logic devices such as field-programmable gate arrays (FPGAs) are useful for a wide range of applications. However, FPGAs are not commonly used in battery-powered applications because they consume more power than application-specified integrated circuits and lack power management features. In this paper, we describe the design and implementation of Pika, a low-power FPGA core targeting battery-powered applications. Our design is based on a commercial low-cost FPGA and achieves substantial power savings through a series of power optimizations. The resulting architecture is compatible with existing commercial design tools. The implementation is done in a 90-nm triple-oxide CMOS process. Compared to the baseline design, Pika consumes 46% less active power and 99% less standby power. Furthermore, it retains circuit and configuration state during standby mode and wakes up from standby mode in approximately 100 ns

Scheduling designs into a time-multiplexed FPGA

An algorithm is presented for partitioning a design in time. The algorithm devides a large, technology-mapped design into multiple configurations of a time-multiplexed FPGA. These configurations are rapidly executed in the FPGA to emulate the large design. The tool includes facilities for optimizing the partitioning to improve routability, for fitting the design into more configurations than the depth of the critical path and for compressing the critical path of the design into fewer configurations, both to fit the design into the device and to improve performance. Scheduling results are shown for mapping designs into an 8-configuration time-multiplexed FPGA and for architecture investigation for a time-multiplexed FPGA.

A 90-nm Low-Power FPGA for Battery-Powered Applications

Programmable logic devices such as field-programmable gate arrays (FPGAs) are useful for a wide range of applications. However, FPGAs are not commonly used in battery-powered applications because they consume more power than application-specified integrated circuits and lack power management features. In this paper, we describe the design and implementation of Pika, a low-power FPGA core targeting battery-powered applications. Our design is based on a commercial low-cost FPGA and achieves substantial power savings through a series of power optimizations. The resulting architecture is compatible with existing commercial design tools. The implementation is done in a 90-nm triple-oxide CMOS process. Compared to the baseline design, Pika consumes 46% less active power and 99% less standby power. Furthermore, it retains circuit and configuration state during standby mode and wakes up from standby mode in approximately 100 ns

Trusted design in FPGAs

Using FPGAs, a designer can separate the design process from the manufacturing flow. Therefore, the owner of a sensitive design need not expose the design to possible theft and tampering during its manufacture, dramatically simplifying the process of assuring trust in that design. Modern FPGAs include bitstream security features that turn the fielded design trust problem into an information security problem, with well-known cryptographic information security solutions. The generic nature of the FPGA base array allows the validation expense to be amortized over all designs targeted to that base array. Even the task of checking design tools is simplified by using non-destructive checks of the FPGA design.

Determination of Power Gating Granularity for FPGA Fabric

In this study, we present a design methodology to determine the granularity of power gating for field programmable gate arrays (FPGAs). Fine-grain power gating is more effective than coarse-grain power gating to reduce the active leakage power of unused logic and interconnection resources. However, the area overhead in fine-grain power gating is higher than that of coarse-grain power gating. Based on the placement and routing of benchmark designs in Spartan-3trade-like FPGA, guidelines for determining the granularity of power gating are provided. It is found that programmable resources with low utilization can be power gated more coarsely than the resources with high utilization

A 12 Gbps DES Encryptor/Decryptor Core in an FPGA

This paper describes two implementations of a Data Encryption Standard (DES) encryptor/decryptor that operate at data rates up to 12 Gbps. The 12 Gpbs number is faster than any previously published design. In these DES implementations, the key can be changed and the core switched from encryption to decryption mode on a cycle-by-cycle basis with no dead cycles. The designs were synthesized from Verilog HDL and implemented in Xilinx XCV300 and XCV300E devices. This paper describes the optimizations used and the coding conventions required to direct the synthesis tools to map the design to achieve a high-speed implementation. No physical constraints were given to the tools.

Placement-based partitioning for lookup-table-based FPGAs

Lookup-table-based field-programmable gate array (FPGA) logic blocks contain multiple lookup-tables, flip flops, and other features. The partitioning of this logic into physical blocks has a logical component, traditionally handled as part of technology mapping in logic synthesis, and a physical component, traditionally handled by placement in physical design. However, methods that use a purely logical partitioning give designs that are difficult to route, and methods that use a purely physical partitioning do not result in legal logical blocks. The authors describe a partitioning method that includes both logic-based and placement-based steps to achieve a high-quality legal partitioning. The method simultaneously generates an initial placement for the design.<<ETX>>

Architecture issues and solutions for a high-capacity FPGA

High-capacity FPGAs pose device architects with a variety of problems.The most obvious of theseproblems is interconnect capacity. Others include interconnect performance, clock distribution and IO capacity. This paper describes these problems and the solutions to these problems chosen in the Xilinx XC4000EX family architecture.

Design, synthesis and evaluation of heterogeneous FPGA with mixed LUTs and macro-gates

Small gates, such as AND2, XOR2 and MUX2, have been mixed with lookup tables (LUTs) inside the. programmable logic block (PLB) to reduce area and power and increase performance in FP-GAs. However, it is unclear whether incorporating macro-gates with wide inputs inside PLBs is beneficial. In this paper, we first propose a methodology to extract a small set of logic functions that are able to implement a large portion of functions for given FPGA applications. Assuming that the extracted logic functions are implemented by macro-gates in PLBs, we then develop a complete synthesis flow for such heterogeneous PLBs with mixed LUTs and macro-gates. The flow includes a cut-based delay and area optimized technology mapping, a mixed binary integer and linear programming based area recovery algorithm to balance the resource utilization of macro-gates and LUTs for area-efficient packing, and a SAT-based packing. We finally evaluate the proposed heterogeneous FPGA using the newly developed flow and show that mixing LUT and macro-gates, both with 6 inputs, improves performance by 16.5% and reduces logic area by 30% compared to using merely 6-input LUTs.