1,720,991 research outputs found
Time-to-Digital Converter IP-Core for FPGA at State of the Art
Full text linkThe Field Programmable Gate Array (FPGA) structure poses several constraints that make the implementation of complex asynchronous circuits such as Time-Mode (TM) circuits almost unfeasible. In particular, in Programmable Logic (PL) devices, such as FPGAs, the operation of the logic is usually synchronous with the system clock. However, it can happen that a very high-performance specifications demands to abandon this paradigm and to follow an asynchronous implementative solution. The main driver forcing the use of programmable logic solutions instead of tailored Application Specific Integrated Circuits (ASIC), best suiting an asynchronous design, is the request coming from the research community and industrial RD of fast-prototyping at low Non Recursive Engineering (NRE) costs. For instance in the case of a high-resolved Time-to-Digital Converter (TDC), a signal clocked at some hundreds of MHz implemented in FPGA allows implementing a TDC with resolution at ns. If a higher resolution is required, the signal frequency cannot be increased further and one of the aces up the designer's sleeve is the propagation delay of the logic in order to quantize the time intervals by means of a so-called Tapped Delay-Line (TDL). This implementation of TDL-based TDC in FPGAs requires special attention by the designer both in making the best use of all available resources and in foreseeing how signals propagate inside these devices. In this paper, we investigate the implementation of a high-performance TDL-TDC addressed to 28-nm 7-Series Xilinx FPGA, taking into account the comparison between different technological nodes from 65-nm to 20-nm. In this context, the term high-performance means extended dynamic-range (up to 10.3 s), high-resolution and single-shot precision (up to 366 fs and 12 ps r.m.s respectively), low differential and integral non-linearity (up to 250 fs and 2.5 ps respectively), and multi-channel capability (up to 16)
Cross-Talk Issues in Time Measurements
Full text linkThe enormous diffusion of Time-Mode circuits, in particular Time-to-Digital Converter (TDC) time measurement circuits, and at the same time the dizzying increase in parallel channels required by the most recent applications, for example in the automotive and digital imaging fields, brings the problem of electromagnetic interference between channels ever more to the fore. This phenomenon, generally known as Cross-Talk (XT), is particularly critical given the increase in the operating frequency and density of systems components, and its effect on the timing parameters in TDC measurements is investigated. Considering the time measurements, XT creates temporal shift on the physical events from which the timestamps are extracted; in this manner, an error in the measurements is generated. In order to detect the XT phenomena, a methodical analysis based on Code-Density Test (CDT) is performed; in this terms, two different typologies of XTs are investigated, which are correlated and uncorrelated XT. Furthermore, a TDC board is used as case study and all the XT sources are detected and classified. Thus, a classification of the importance of the different sources of XT is achieved and a solution to minimize the different causes is proposed
Digital Instrument for Time Measurements: Small, Portable, High-Performance, Fully Programmable
Full text linkWe present a small, portable, plug-and-play time measurement instrument entirely based on Field Programmable Gate Array (FPGA). Its performance is state-of-the-art in terms of the most recent Application-Specific Integrated Circuit (ASIC) solutions of Time-to-Digital Converters (TDCs), and all operating features are fully-programmable. The instrument offers an excellent cost-performance and is suitable for detector test and time correlation measurement applications. More generally, the instrument is very well suited for fast-prototyping of systems where time measures are involved, at low cost and design effort. All the features of the instrument can be easily accessed through either the Graphical User Interface (GUI) or directly from the software Application Programming Interface (API)
Complete System-on-Chip Linux-based Platform for Measurement and Generation of Time Domain Signals
No full textIn this contribution we present a novel implementation of a bundle hardware, firmware and software for the measurement and generation of time domain signals, based on a custom System-on-Chip Linux-based platform. Recently, many solutions have been already proposed both by the industry and by the academia for the measurement and generation of time events, in the forms of full-custom Application-Specific Integrated Circuits and Field Programmable Gate Array IP-Cores. However, while these solutions have proven themselves mostly satisfying in terms of performance, they often lack ease of use, upgrade and interfacing. Indeed, while those implementations are flexible and can be fully customized, integrating them in existing systems is usually, if not always, challenging. To solve these issues, we present here a hybrid hardware and software implementation of Time-to-Digital Converters and Digital-to-Time Converters in Programmable Logic. The main feature is the simplified, yet efficient, interface to other user logic or to the ARM core in the Xilinx Zynq-7000 System-on-Chips, which hosts a Linux-based Operating System. The interfacing of the two worlds is eased by a set of IP-Cores and libraries, so that the performance of the Programmable Logic part can be used and connected easily with the more flexible and user-friendly Processing System. This opens new opportunities, like the use of the Linux Operating System for simple transfer of data through advanced interfaces and protocols, without requiring complex hardware on the Programmable Logic part
Synchronization in Networks of Time-to-Digital Converters based on Field Programmable Gate Arrays
No full textNowadays, in many high technological fields of research the classical Time-to-Digital-Converter (TDC) structure is no more satisfactory, since the architecture of one measuring unit connected to many sensors is no more feasible because the not sufficient number of channels, the lack of flexibility or both. This is the case, for instance, of Positron Emission Tomography (PET) facilities of last generation.In the Nuclear Science Symposium 2018 we presented a "All-Digital Fully-Configurable Instrument for Multi-Channel Time Measurements at High Performance". The present contribution deals with the implementation of a distributed architecture of TDCs, i.e. an instrument that allows measuring timestamps on different devices but with the same relative time reference. This allows managing measures performed by different TDCs like if they were collected by a unique device, so providing a huge flexibility that opens the way for new advanced applications like PET network detectors.The realization of a network for TDCs poses two main issues: a high-performance data transfer mechanism in addition to a precise and reliable synchronization methodology. This contribution focuses on the latter issue that is the most critical and complex to address. The analysis is carried out both from theoretical and implementation point of view
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Time-Mode analysis of Crosstalk interference in a FPGA-based TDC implementation
No full textIn modern electronic systems and telecommunication applications, crosstalk (XT) has become a serious problem, especially in very high-speed, multi-channel, and high-density circuits. Crosstalk interference is an unwanted electromagnetic energy sharing between a node (aggressor) and a signal carrying information (victim). If the interference is strong enough, the receiver reads a corrupted information. In Time-Mode (TM) circuits and in time-based experiments, where the information is represented as the time distance between signals, the induced electromagnetic energy is converted in a temporal shift of the edges of the waves degrading the information or the measurements respectively. In this sense, Time-to-Digital Converters (TDCs) are the building blocks of TM circuits and the principal actors in time-based experiments. In fact, a TDC has the role to convert into a digital code a time interval. Nowadays, market asks for higher and higher number of channels maintaining the performance of the systems. A limiting factor to achieve this result is exactly the XT, and therefore it is necessary to study the sources of interference to minimize electromagnetic sharing. In this contribution, we classify and investigate the effects and the causes of crosstalk in time measurements considering a multi-channel TDC implemented in Field Programmable Gate Array (FPGA) as case study, deriving design rules for minimizing the related effects
Multi-Channel High-Resolution Pulse-Width Modulation IP-Core Implementation for FPGA and SoC Device
No full textIn this contribution we present a novel implementation of a Pulse-Width Modulation (PWM) IP-Core in a Field-programmable Gate Array device (FDPGA), whose main feature is the generation of high-frequency and high-resolution Pulse-Width Modulation waves using very low amount of resources. The IP-Core is suited for any Xilinx 7-Series Field-Programmable Gate Array and System-on-Chip (SoC) and has been successfully validated on an Avnet Mini-Module Plus, which hosts a Xilinx Kintex-7 XC7K325T-1.This IP-Core reaches exceptionally high Full-Scale Ranges while keeping still a very high resolution and precision, thanks to the use of the Nutt technique. A high-frequency digital counter is used to provide a coarse part of a time wave, while the use of IDELAYE2 primitives brings down the system resolution while keeping large Full-Scale Range. Indeed, the maximum resolution on a-2/-3 speed grade device is 39 ps with precision below 16.5 ps r.m.s. over Full-Scale Range of 1.30 ms. The overall logic resources required to implement this module consist of a very low number of IDELAYE2 and other standard components, which allow the instantiation of up to 64 channels in a single Kintex-7 XC7K325T-1.The Pulse-Width Modulation IP-Core offers an ARM Advanced eXtensible Interface slave port, which allows an easy and efficient configuration both from custom programmable logic and from microprocessors, like ARM or Microblaze cores. A dual set of configuration registers is available to the user, which permits a glitch-less configuration, synchronized with the user writing on the slave port or with external events on the module I/O ports
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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