一种片上系统(SOC)时钟同步设计方法

SoC设计很大程度上依赖于IP核的可重用性。由于各IP核中时钟延时的不同，要将IP核集成到一个同步SoC中时钟分布变得很难。本文介绍了一种SoC时钟同步设计方法，这种方法将可调节延时的时钟电路插入在时钟分布网络中．以取得时钟边沿的匹配和同步。使用可调节电路进行时序调整，减少了设计迭代时间，节约了设计成本。     

一种改进的高速彩票总线仲裁器

随着半导体工艺的发展,片上系统(System-on-Chip, SoC)内部集成的不同功能IP(Intellectual Property)核越来越多。各IP核通过总线方式连接,多核同时抢占总线很大地制约了片上系统的性能。高效的总线仲裁器可以解决多核抢占总线引起的冲突和竞争问题,提升片上系统性能。该文提出一种改进的高速彩票总线仲裁器。使用4相双轨协议代替时钟实现彩票抽取机制以防止彩票丢弃,采用异步流水线交叉并行的工作方式以提升工作速度。在NINP(NonIdling and NonPreemptive)模型下通过65 nm CMOS工艺的Xilinx Virtex5板级验证,相比经典彩票仲裁器和动态自适应彩票仲裁器,具有更好的带宽分配功能,有效避免撑死和饿死现象,工作速度提高49.2%以上,具有一定的功耗优势,适用于有速度要求的多核片上系统。     

基于开源IP核的视频解码SoC平台研究

文章设计了一款基于开源IP核的SoC视频解码平台,该平台中使用的IP均经过了CQIP系统的严格评测,并在Xilinx公司的FPGA上进行了验证,实验结果证明该系统具有良好的实时性和较低的功耗,非常适合于便携式设备。     

Design for Consecutive Testability of System-on-a-Chip with Built-In Self Testable Cores

This paper introduces a new concept of testability called consecutive testability and proposes a design-for-testability method for making a given SoC consecutively testable based on integer linear programming problem. For a consecutively testable SoC, testing can be performed as follows. Test patterns of a core are propagated to the core inputs from test pattern sources (implemented either off-chip or on-chip) consecutively at the speed of system clock. Similarly the test responses are propagated to test response sinks (implemented either off-chip or on-chip) from the core outputs consecutively at the speed of system clock. The propagation of test patterns and responses is achieved by using interconnects and consecutive transparency properties of surrounding cores. All interconnects can be tested in a similar fashion. Therefore, it is possible to test not only logic faults but also timing faults that require consecutive application of test patterns at the speed of system clock since the consecutively testable SoC can achieve consecutive application of any test sequence at the speed of system clock.     

Constructing IP cores’ transparency paths for SoC test access using greedy search

Today’s SoC design demands efficient test access mechanism to develop and perform manufacturing test. Transparency based methods have their advantages for IP cores’ test reuse in SoC level. In this paper, an IP core transparency paths construction approach employing greedy search strategy based on gate-level heuristic information is proposed. With these transparency paths, IP cores can consecutively transfer one test per clock cycle from their inputs to outputs, and thus can be used in transparency-based test scheme to benefit at-speed testing and decrease the demand of parallel TAMs. The experimental results show lower extra overhead needed in our approach than conventional boundary scan and previous RT level approaches.     

SoC interconnection protection through formal verification

The wide adoption of third-party hardware Intellectual Property (IP) cores including those from untrusted vendors have raised security concerns for system designers and end-users. Existing approaches to ensure the trustworthiness of individual IPs rarely consider the entire SoC design, especially the IP interactions through SoC bus. These methods can hardly identify malicious logic (or design flaws) distributed in multiple IPs whereas individual IPs fulfill security properties and can pass the security testing/verification. One possible solution is to treat the SoC as one IP core and try to verify security properties of the entire design. This method, however, suffers from scalability issues due to the large size of SoC designs with multiple IP cores integrated. In this paper, we present a scalable SoC bus verification framework trying to verify the security properties of SoC bus implementation where the bus protocol plays the role of the golden reference. More specifically, finite state machine (FSM) models will be constructed from the bus implementation and the trustworthiness will be verified based on the property set derived from the bus protocol and potential security threats. Along with IP level formal verification solutions, the proposed framework can help ensure the security of large-scale SoCs. Experimental results on ARM AMBA Bus demonstrate that our approach is applicable and scalable to prevent information leakage and denial-of-service (DoS) attack by verifying security properties.     

SoC低功耗设计及其技术实现

文章根据低功耗设计理论和方法,分别从系统级、模块级及RTL级三个层次上考虑一款SoC芯片功耗设计。在系统级采用工作模式管理方式,在模块级采用软件管理的方式,RTL级采用门控方式,三种方式的应用大大降低芯片了的功耗。仿真分析表明,该芯片的低功耗设计策略取得了预期的效果,实现了较低的动态功耗与很低的静态功耗。该SoC采用0．18μm CMOS工艺库实现,面积为7．8mm×7．8mm,工作频率为80Mnz,平均功耗为454．268mW。     

用于SoC的SPI接口设计与验证

给出了一个可用于SoC设计的SPI接口IP核的RTL设计与功能仿真。采用AMBA2．0总线标准来实现SPI接口在外部设备和内部系统之间进行通信,在数据传输部分,摒弃传统的需要一个专门的移位传输寄存器实现串／并转换的设计方法,采用复用寄存器的方法,把移位传输寄存器和发送寄存器结合在一起,提高了传输速度,也节约了硬件资源。采用SoC验证平台进行SoC环境下对IP的验证,在100MHz时钟频率下的仿真和验证结果表明,SPI接口实现了数据传榆,且满足时序设计要求。     

基于V93000的SoC中端口非测试复用的ADC和DAC IP核性能测试方案

 SoC(System-on-a-Chip)芯片设计中,由于芯片测试引脚数目的限制以及基于芯片性能的考虑,通常有一些端口不能进行测试复用的IP(Intellectual Property)核将不可避免地被集成在SoC芯片当中.对于端口非测试复用IP核,由于其端口不能被直接连接到ATE(Automatic Test Equipment)设备的测试通道上,由此,对端口非测试复用IP核的测试将是对SoC芯片进行测试的一个重要挑战.在本文当中,我们分别提出了一种基于V93000测试仪对端口非测试复用ADC(Analog-to-Digital Converter)以及DAC(Digital-to-Analog Converter)IP核的性能参数测试方法.对于端口非测试复用ADC和DAC IP核,首先分别为他们开发测试程序并利用V93000通过SoC芯片的EMIF(External Memory Interface)总线对其进行配置.在对ADC和DAC IP 核进行配置以后,就可以通过V93000捕获ADC IP 核采样得到的数字代码以及通过V93000 采样DAC IP 核转换得到的模拟电压值,并由此计算ADC以及DAC IP 核的性能参数.实验结果表明,本文分别提出的针对端口非测试复用ADC以及DAC IP 核测试方案非常有效.     

一种适用于SoC的时钟复位管理电路设计

给出了一套适用于SoC芯片的时钟和复位管理电路设计范例,详细介绍了SoC芯片中的时钟和复位管理电路的实现方案。其中时钟管理电路支持输入时钟可选、PLL动态变频、时钟门控管理和时钟状态查询功能,能够灵活的控制各模块输入时钟开启或关闭,很好的支持SoC芯片低功耗工作模式。复位管理电路支持复位输入控制功能和复位状态查询功能。复位输入控制可以选择使能或不使能复位源触发系统复位。     

Design and Application of Adaptive Delay Sequential Elements

Lower operating voltages and faster clock frequencies in advanced fabrication processes increase the circuit delay sensitivity to voltage, temperature, and process variations and modeling approximations. Uncorrelated delay variations along data and clock paths cause timing violations. In this paper, we propose a method for correcting timing violations by in-circuit tuning of clock latencies after fabrication. We introduce adaptive delay sequential elements (ADSEs) that use charge storage on pMOS floating gates to tune the clock latencies of timing critical flip-flops. ADSEs facilitate in-circuit optimization of clock latencies under varying operating conditions. ADSE tuned clock latencies are nonvolatile and can be repeatedly adjusted after fabrication using only electrical signals. We present examples of implicit and explicit pulsed ADSEs and their tuning operations. Our experiments with fabricated prototypes show that ADSEs can tune their clock latencies with picosecond resolution over one-half of the clock period. Our experiments also show that ADSE sensitivities to supply voltage, temperature, noise, and transistor mismatch are comparable to nonadaptive sequential elements. We present experimental data that show ADSE tuned delays change only 15% after ten years at 125degC. We propose a method for selective tuning of embedded ADSEs and demonstrate its application in a fabricated prototype. ADSEs can selectively replace timing-critical flip-flops of a circuit with negligible area impact     

Design methodology for synthesizing clock distribution networksexploiting nonzero localized clock skew

An integrated top-down design methodology is presented in this brief for synthesizing high performance clock distribution networks based on application dependent localized clock skew. The methodology is divided into four phases: (1) determining an optimal clock skew schedule composed of a set of nonzero clock skew values and the related minimum clock path delays; (2) designing the topology of the clock distribution network with delays assigned to each branch based on the circuit hierarchy, the aforementioned clock skew schedule, and minimizing process and environmental delay variations; (3) designing circuit structures to emulate the delay values assigned to the individual branches of the clock tree; and (4) designing the physical layout of the clock distribution network. The clock distribution network synthesis methodology is based on CMOS technology. The clock lines are transformed from distributed resistive capacitive interconnect lines into purely capacitive interconnect lines by partitioning the RC interconnect lines with inverting repeaters. Variations in process parameters are considered during the circuit design of the clock distribution network to guarantee a race-free circuit. Nominal errors of less than 2.5% for the delay of the clock paths and 7% for the clock skew between any two registers belonging to the same global data path as compared with SPICE Level-3 are demonstrated     

降低系统芯片中跨时钟域设计和验证复杂度的方法

在系统芯片设计中,直接采用现有的跨时钟域信号处理方法不仅设计复杂度高而且验证难度大.为了解决这个问题,将跨时钟域设计与功能设计完全分离,在每个通信接口部件中采用独立的、专用的跨时钟域处理模块统一解决跨时钟域信号的传输问题,并通过封装点对点通信接口和合并处理同一方向的跨时钟域信号,将需要处理的跨时钟域信号的数量减少为方向相反的2组.实验结果表明,该方法能够有效降低跨时钟域设计的验证难度和系统芯片的设计复杂度,并且不会明显增加功能部件的传输延迟和面积开销.     

系统芯片的关键技术及发展方向

系统芯片,即(SoC),将包含处理器、存储器和片上逻辑等的一个系统集成在单一的芯片上。SoC所特有的功能强、速度高、体积小、成本低、功耗低等优点使得其技术不断发展,应用越来越广泛。文章首先探讨了系统芯片(SoC)的特点及分类,接着详细阐述了开发SoC所需IP核设计与复用、软硬件协同设计、软硬件协同设计等关键技术。分析了基于平台设计方法的优点,并介绍了SoC的一体化测试流程、共时测试等SoC测试新技术。     

The effect of propagation delay uncertainty on the speed oftime-of-flight digital optoelectronic circuits

Time-of-flight synchronization is a new digital design methodology for optoelectronics that eliminates latches, allowing higher clock rates than alternative timing schemes. Synchronization is accomplished by precisely balancing connection delays. Circuits use pulse-mode signaling and clock gates to restore pulse timing. Many effective pipeline stages are created within combinational logic without extra hardware bounding the stages. Time-of-flight design principles are applicable to packet routing and sorting processors for optical interconnection networks. Circuits are unique because the clock rate is limited primarily by imprecision in propagation delay rather than absolute delay, as in circuits with latches. We develop a general model of delay uncertainty and focus on the effect that static and dynamic uncertainty accumulated over circuit paths has on the minimum feasible clock period. We present a method for traversing the circuit graph representation of a time-of-flight circuit to compute arrival time uncertainty at each pulse interaction point. Arrival time uncertainties give rise to pulse width and overlap constraints. From these constraints we formulate a constrained minimization to find the minimum clock period. We demonstrate our method on circuits implemented with 2×2 electro-optic switches and optical waveguides and find the electronic component of path uncertainty frequently limits speed     

Delay fault testing of IP-based designs via symbolic path modeling

Predesigned blocks called intellectual property (IP) cores are increasingly used for complex system-on-a-chip (SoC) designs. The implementation details of IP cores are often unknown or unavailable, so delay testing of such designs is difficult. We propose a method that can test paths traversing both IP cores and user-defined blocks, an increasingly important but little-studied problem. It models representative paths in IP circuits using an efficient form of binary decision diagram (BDD) and generates test vectors from the BDD model. We also present a partitioning technique, which reduces the BDD size by orders of magnitude and makes the proposed method practical for large designs. Experimental results are presented that show that it robustly tests selected paths without using extra logic and, at the same time, protects the intellectual contents of IP cores     

一种兼容AMBA总线的实时高效静态存储管理IP的设计与实现

设计了一种兼容AMBA2.0AHB总线的实时高效存储管理IP——静态存储管理IP.与虚拟存储管理技术相比,IP可以为实时系统芯片的高实时性提供良好的保障,它完成一次存储器访问最多需要2个时钟延时,最少可以达到0延时传输.同时它具有结构简单、可支持8个64M的静态存储器、可编程控制以及进行不同数据宽度的Burst传输等特点.设计采用结构完全并行、时序完全同步的状态机设计思想,采用SIMC.18工艺进行流片,系统芯片整体面积为5mm×3.5mm,测试结果与设计目标基本一致.     

SoC新技术--可编程逻辑IP核

随着半导体技术的飞速发展,单个硅片上的集成度越来越高,SoC(System-On-a-Chip）已成为IC(Integrated Circuit）设计技术的主流。由于市场竞争的日益激烈,TTM(Time to Market）已成为一个非常重要的因素,直接影响到产品的市场份额和开发商的利润。如何更快、更有效的完成SoC设计逐渐成为人们关注的焦点。可编程逻辑IP核技术的出现有效的缩短了SoC的设计周期并使得芯片设计更具灵活性。本文将对这种技术进行详细的介绍。     

高清晰度数字视频SDI卡的设计

在研究了SDI串行数字接口工作原理的基础上,提出了一种新型的高清晰度/标准清晰度数字电视信号采集传输用的SDI卡,阐述了SDI卡中的DVI输入接口、均衡电路、串并转换电路、并串转换电路、输出驱动电路和可编程时钟电路的设计,在硬件设计基础上介绍了FPGA中IP核设计和上位机程序设计方法和流程,并总结了开发调试中需要注意的问题.高清晰度数字视频SDI卡通过实际测试,实现了DVI、HD和SD信号的输入处理和输出转换,验证了设计方案的效果.     

SoC片上总线技术的研究

在SoC设计中,经常会遇到一些问题,包括IP核移植性、设计复用、设计验证,以及公共设计平台的搭建。如何有效地解决这些问题,使得设计SoC系统就像设计微机系统那样方便快捷,这就是片上总线系统提出的目的。本文通过对AMBA, AVALON, OCP,WISHBONE等SoC总线的比较,分析了SoC片上总线技术。