cadence仿真流程
cadenceic基础仿真经典实用
• 选择分析模式：
•cadence ic 基础仿真
• 电路中有两个电压源，一个用作VDD,另一个用作信号输入 Vin
V in
•cadence ic 基础仿真
• 输出的选择
•cadence ic 基础仿真
• 分析一阶共源放大器获得的波形图 • 波形图显示了当Vin 从0->2V 时输出的变化
•cadence ic 基础仿真
• 下图为以温度为变量进行直流分析时候的波形图
•cadence ic 基础仿真
带隙基准的温度参考
•cadence ic 基础仿真
•cadence ic 基础仿真
•cadence ic 基础仿真
•cadence ic 基础仿真
实例5 一阶放大器
共源的一阶放大器
• 下图显示了为仿真产生的输出日志文件 •
•cadence ic 基础仿真
• 产生的波形如下所示：
•cadence ic 基础仿真
• 可以通过设定坐标轴来获得电流—电压曲线 • 按以下方式进行： Axis-> X Axis
•cadence ic 基础仿真
• 按下图所示，将X轴设定为二极管上的电压 降
•cadence ic 基础仿真
• 在改变了X轴之后，波形应如下图所示：
•cadence ic 基础仿真
• 由于我们只对二极管的伏安特性曲线感兴趣，因此我们可以只选择流 经二极管的电流与其两端压降。新的曲线如下图所示：
•cadence ic 基础仿真
实例2 双极型晶体管的伏安特性曲线
• 首先为双极型晶体管电路新建一个cell view • 利用原理图编辑所需要的仿真电路
然后单击ESC。 • 可以得到如下图所示的一族伏安特性曲线
cadence教程
cadence教程Cadence 是一款流行的电路设计和仿真工具。
它广泛应用于电子工程领域，可以帮助工程师进行电路设计、布局、仿真和验证。
以下是一个简单的 Cadence 教程，帮助你快速入门使用该软件。
第一步: 下载和安装 Cadence首先，你需要从 Cadence 官方网站下载适用于你操作系统的Cadence 软件安装包。
在下载完成后，双击安装包文件并按照安装向导的指示进行安装。
第二步: 创建新项目打开 Cadence 软件后，你将看到一个初始界面。
点击“File”菜单，然后选择“New”来创建一个新的项目。
第三步: 添加电路元件在新项目中，你可以开始添加电路元件。
点击菜单栏上的“Library”按钮，然后选择“Add Library”来添加一个元件库。
接下来，使用菜单栏上的“Place”按钮来添加所需的电路元件。
第四步: 连接电路元件一旦添加了电路元件，你需要使用连线工具来连接它们。
点击菜单栏上的“Place Wire”按钮，然后将鼠标指针移到一个元件的引脚上。
点击引脚，然后按照电路的设计布局开始连接其他元件。
第五步: 设置仿真参数在完成电路布局后，你需要设置仿真参数。
点击菜单栏上的“Simulate”按钮，然后选择“Configure”来设置仿真器类型、仿真时间等参数。
第六步: 运行仿真设置完成后，你可以点击菜单栏上的“Simulate”按钮，然后选择“Run”来运行仿真。
仿真过程会模拟电路的运行情况，并生成相应的结果。
总结通过这个简单的 Cadence 教程，你了解了如何下载安装Cadence 软件、创建新项目、添加电路元件、连接元件、设置仿真参数和运行仿真。
掌握了这些基本操作后，你可以进一步学习和探索 Cadence 的更多功能和高级技巧。
祝你在使用Cadence 中取得成功！。
cadence后仿教程
默认第一项是 spectre,意味着 INV_example_tes t里调用的是 INV_example的 schmatic view来 进行仿真
如要进行后仿我们得 修改Switch View List, 把calibre加在spectre 前面,意味着仿真的时 候INV_example_test 调用INV_example的 calibre view来进行仿 真,这就是后仿!!!
<3>指定提取哪些节点的寄生参数： 默认是ALL Nets（提取所有节点） 也可以自定义（Specified Nets）：可以提取除了指
定节点以外的所有节点（Exclude），也可以只提取指定的 节点（Include），在相应的文本框里写入节点的net名即 可，或者点击右侧的小箭头，然后在弹出的原理图里选择你 想输入的节点，按ESC键，你所选择的节点名就自动填在左 侧文本框中．
至此,我们仍未进行后仿,我们只是提取出 了寄生参数,并生成了带这些寄生参数的 calibre view,这都是为后仿做准备. 接下来介绍如何后仿.
方法一
1.打开测试平台,此 例是 INV_example_test. 2.打开ADE (仿真环 境)窗口 3.与仿真原理图不 同的是多出这一步: 点击Setup— >Environment 弹出一个配置窗口 (见下页)
6.Run PEX
弹出两个框：一个 是Calibre View配 置对话框（左 图），一个是寄生 参数文本（见下 页）． 注意左边两个设 置，其他默认即 可．
6.Run PEX
第一次运行PEX会弹 出映射文件向导， 引导大家生成 MAP文件． 以后就不用设置了． 除了寄生电阻寄生电 容以外，所有器件 都用st02中的模型 来映射．
CAdence16.6PSpice1，使用自带例程进行第一个仿真
CAdence16.6PSpice1，使⽤⾃带例程进⾏第⼀个仿真1、建⽴原理图选择如下
2、新建⼀个⼯程，如下：
3、上图点击OK，进⼊界⾯，界⾯有下拉框，以放⼤器为例
4
5、发现⼯程⾥边⾃带如下：
6、点击1处，弹出2的参数会话框
7、点击第⼀张图，开始运⾏
8、弹出新的，运⾏结果如下：
在7界⾯更改了参数以后，只需要在8的界⾯点击运⾏就能看到新的波形了
9、可以在红圈位置直接删除不想看到的，点击选中，delete
10、点击1，在2位置添加想看到的曲线
例如看功率如下
11、如何看功率最⼤值，打击1，2处选择函数，3处选中要看的
得到结果如下
12、点击如下按钮，让此界⾯永远处于最上，之后让界⾯像第⼆张图这样
13、我们此时可以移动原理图的探针，我们会发现，波形跟着实时改变
14、⽣成报告。
window--copy to clipboard，之后在word⾥边可以直接粘贴。
15、通过点击如下按钮，能看到直流静态⼯作点、直流静态电流，功耗。
CADENCE仿真流程
CADENCE仿真流程1.设计准备在进行仿真之前，需要准备好设计的原理图和布局图。
原理图是电路的逻辑结构图，布局图是电路的物理结构图。
此外，还需要准备好电路的模型、方程和参数等。
2.确定仿真类型根据设计需求，确定仿真类型，包括DC仿真、AC仿真、时域仿真和优化仿真等。
DC仿真用于分析直流电路参数，AC仿真用于分析交流电路参数，而时域仿真则用于分析电路的时间响应。
3.设置仿真参数根据仿真类型，设置仿真参数。
例如，在DC仿真中，需要设置电压和电流源的数值；在AC仿真中，需要设置信号源的频率和幅度；在时域仿真中，需要设置仿真的时间步长和仿真时间等。
4.模型库选择根据设计需求，选择合适的元件模型进行仿真。
CADENCE提供了大量的元件模型，如晶体管、二极管、电感、电容等。
5.确定分析类型根据仿真目标，确定分析类型，例如传输功能分析、噪声分析、频率响应分析等。
6.仿真运行在仿真运行之前，需要对电路进行布局和连线。
使用CADENCE提供的工具对电路进行布局和连线，并生成物理设计。
7.仿真结果分析仿真运行后，CADENCE会生成仿真结果。
利用CADENCE提供的分析工具对仿真结果进行分析，观察电路的性能指标。
8.优化和修改根据仿真结果，对电路进行优化和修改。
根据需要，可以调整电路的拓扑结构、参数和模型等，以改进电路的性能。
9.再次仿真和验证根据修改后的电路，再次进行仿真和验证，以确认电路的性能指标是否得到改善。
最后需要注意的是，CADENCE仿真流程并不是一成不变的，根据具体的设计需求和仿真目标，流程可能会有所调整和修改。
此外，CADENCE还提供了许多其他的工具和功能，如电路板设计、封装设计、时序分析等，可以根据需要进行使用。
CADENCE仿真步骤
CADENCE仿真步骤
Cadence是一款电路仿真软件，它可以帮助设计师创建、分析和仿真
电子电路。
本文将介绍Cadence仿真的步骤。
1.准备仿真结构：第一步是准备仿真结构。
我们需要编写表示电路的Verilog或VHDL代码，然后将它们编译到Cadence Integrated Circuit (IC) Design软件中。
这会生成许多文件，包括netlist和verilog等文件，这些文件将用于仿真。
2.定义仿真输入输出信号：接下来，我们需要定义仿真的输入信号和
输出信号。
输入信号可以是电压、电流、时间和其他可测量的变量。
我们
需要定义输入信号的模拟和数字值，以及输出信号的模拟和数字值。
3.定义参数：参数是仿真中用于定义仿真设计的变量，这些变量可以
是仿真中电路的物理参数，如电阻、电容、时延、输入电压等，也可以是
算法参数，如积分步长等。
4.运行仿真：在所有参数和信号都设置完成后，我们可以运行仿真。
在运行仿真之前，可以使用自动参数检查来检查参数是否正确。
然后，使
用“开始仿真”命令即可启动仿真进程。
5.结果分析：在仿真结束后，我们可以使用结果分析器来查看输出信
号的模拟和数字值，以及仿真中电路的其他特性，如暂态分析、稳态分析、功率分析等。
以上就是Cadence仿真步骤。
Cadence仿真流程
Cadence仿真流程Cadence 仿真流程第⼀章在Allegro 中准备好进⾏SI 仿真的PCB 板图1）在Cadence 中进⾏SI 分析可以通过⼏种⽅式得到结果：Allegro 的PCB 画板界⾯，通过处理可以直接得到结果，或者直接以*.brd 存盘。
使⽤SpecctreQuest 打开*.brd，进⾏必要设置，通过处理直接得到结果。
这实际与上述⽅式类似，只不过是两个独⽴的模块，真正的仿真软件是下⾯的SigXplore 程序。
直接打开SigXplore 建⽴拓扑进⾏仿真。
2）从PowerPCB 转换到Allegro 格式在PowerPCb 中对已经完成的PCB 板，作如下操作：在⽂件菜单，选择Export 操作，出现File Export 窗⼝，选择ASCII 格式*.asc ⽂件格式，并指定⽂件名称和路径（图1.1）。
图1.1 在PowerPCB 中输出通⽤ASC 格式⽂件图1.2 PowerPCB 导出格式设置窗⼝点击图1.1 的保存按钮后出现图1.2 ASCII 输出定制窗⼝，在该窗⼝中，点击“Select All”项、在Expand Attributes 中选中Parts 和Nets 两项，尤其注意在Format 窗⼝只能选择PowerPCB V3.0 以下版本格式，否则Allegro 不能正确导⼊。
3）在Allegro 中导⼊*.ascPCB 板图在⽂件菜单，选择Import 操作，出现⼀个下拉菜单，在下拉菜单中选择PADS 项，出现PADS IN 设置窗⼝（图1.3），在该窗⼝中需要设置3 个必要参数：图1.3 转换阿三次⽂件参数设置窗⼝i. 在的⼀栏那填⼊源asc ⽂件的⽬录ii. 在第⼆栏指定转换必须的pads_in.ini ⽂件所在⽬录（也可将此⽂件拷⼊⼯作⽬录中，此例）iii. 指定转换后的⽂件存放⽬录然后运⾏“Run”，将在指定的⽬录中⽣成转换成功的.brd ⽂件。
cadence版图仿真教程
Tutorial: Simulating HSpice with the Analog Design Environment1.Make directory called something like cadence.$mkdir cadence2.Change to this directory.$cd cadence3.Start the Cadence Design Framework by typing “icfb &” at the command prompt.$icfb&The first window that appears is called the CIW (Command Interpreter Window).Figure 1 – CIW WindowAnother window that appears is the Library Manager. This window allows you to browse the available libraries and create your own.Figure 2 – Library Manager WindowIn the Library Manager, create a new library called EEE534. Select File->New->Library. This will open a new dialog window, in which you need to enter the name of your library, library path, and "Attach to existing tech library." Fill out the form as shown below, then select OK.Figure 3 – Create Library FormYou should see the library "EEE534" appear in the Library Manager.Figure 4 – Library Manager display newly created libraryNext, select the library you just created in the Library Manager and select File->New->Cell View.... We will create a schematic view of an inverter cell. Simply type in "INV" under cell-name and "schematic" under view. Click OK or hit the Enter key. Note: that the "Tool" is automatically set to "Composer-Schematic", the schematic editor.Figure 5 – Create New File FormAlternatively, you could select the "Composer-Schematic" tool, instead of typing out the view name. This will automatically set the view name to "schematic".After you hit "OK", the blank Composer screen will appear.Figure 6 – Virtuoso Schematic EditorTo generate a schematic, you will need to go through the following steps:•From the Schematic Window, choose Add->instance. The Component Browser, will then pop up.•In the Library field, select NCSU_Analog_Parts. We will place the pmos, nmos, vdd, gnd, vdc, vpulse andcap instances in the Schematic Window from the NCSU_Analog_Parts library asinstructed below.Note: pay special attention to the parameters specified in vdc, vpulse, and cap. These parameters are very important in simulation.Place pmos instance•In Component Browser, select P_Transistors and then pmos.•Place it in the Schematic WindowFigure 7 – Add pmos InstancePlace nmos instance•In Component Browser, select N_Transistors and then nmos.•Place it in the Schematic Window.Figure 8 – Add nmos InstancePlace gnd instance•In Component Browser, select Supply_Nets and then gnd.•Place it in the Schematic Window.Figure 9 – Add gnd Instance Place vdd instance•In Component Browser, select Supply_Nets and then vdd •Place it in the Schematic Window.Figure 10 – Add vdd InstancePlace IN pin•From the Schematic Window menu, select Add -> Pin...•In the Pin Name field , enter IN•In the Direction field, select input•Place it in the Schematic WindowFigure 11 – Add Input PinPlace OUT pin•From the Schematic Window menu, select Add -> Pin...•In the Pin Name field , enter OUT•In the Direction field, select output•Place it in the Schematic WindowFigure 12 – Add Output PinPlace vdc instance•In the Component Browser, select Voltage Sources and then vdc •In the DC voltage field, enter 5 V•Place it in the Schematic WindowFigure 13 – Add vdc SourcePlace vpulse instance•In the Component Browser, select Voltage_Sources and then vpulse •Enter the following values in the form:Figure 14 Edit Object vpulse SourcePlace cap instance•In Component Browser, select R_L_C and then cap•In the Capacitance field, enter OutCap F. (This Design Variable will be used in Artist.) •Place it in the Schematic WindowFigure 15 – Add cap InstancePlace wires•In the Schematic Window menu, select Add -> Wire (narrow)•Place wires to connect all the instances•Select Design -> Check and Save.Look at the CIW. You should see a message that says:Extracting “INV schematic”Schematic check completed with no errors.“EEE534 INV schematic” saved.If you do have some errors or warnings, the CIW will give a short explanation of what those errors are. Errors will also be marked on the schematic with a yellow or white box. Errors must be fixed for your circuit to simulate properly. When you find a warning it is up to you to decide if you shouldfix it or not. The most common warnings occur when there is a floating node or when there are wires that cross but are not connected. Just be sure that you know what effect each of these warning will have on your circuit when you simulate.Your schematic should look like the one shown below.Figure 16 – Completed SchematicIf you would like to learn more about the schematic editor, you can work through chapters 1-5 of the Composer Tutorial that comes with the Cadence documentation. Start the documentation browser by typingcdnshelp &at the command prompt. If you find that you cannot view the figures correctly in the web browser, you can click the View/Print PDF link at the top of the page to launch a PDF viewer for the tutorial. This documentation browser offers many more links for you to learn about the Cadence Design Framework.Simulate the Schematic with HSPICE within Virtuoso Analog Design EnvironmentSet up the Simulation EnvironmentYou are now prepared to simulate your circuit.From the Schematic Window menu, select Tools -> Analog Environment. A window will pop-up. This window is the Analog Design Environment Window.Figure 17 - Analog Design Environment WindowChoose a SimulatorFrom the Analog Design Environment menu, select Setup -> Simulator/Directory/Host. Enter the fields as shown below. Choose hspiceS as your simulator. Your simulation will run in the specified Project Directory. You may choose any valid pathname and filename that you like.Figure 18 Choosing Simulator/Directory/Host FormChoose AnalysisWe will setup to do a Transient Analysis on the circuit that we just produced.From the Analog Design Environment menu, select Analyses -> Choose... Fill out the form with the following values:Figure 19 – Choosing AnalysesAdd a VariableFrom the Analog Design Environment menu, select Variables -> Edit. The Editing Design Variables form will appear. Fill out the form as shown below, and then click Add to send this Variable to the Table of Design Variables.(Recall that we entered the OutCap Design Variable in the Capacitor component while editing the schematic in the previous section.)Figure 20 – Editing Design Variables FormSetup OutputWhen using Transient Analysis, the transient voltage will be saved automatically. We can save the current through capacitor C0 in the schematic by doing the following:From the Analog Design Environment menu, select Outputs -> To be Saved -> Select On Schematic In the Schematic Window, click on the lower terminal (not the wire) of capacitor C0.After you click on the terminal, the Analog Design Environment Window should look like this:Figure 21 Analog Design Environment WindownRun SimulationFrom the Analog Design Environment menu, select Simulation -> Run, Look at the echoing information in the CIW window. If the simulation succeeds, the window will display “...successful.”Figure 22 – CIW after simulationIf the simulation is unsuccessful, then one of the error messages should provide a clue as to what went wrong. Remember that you can move elements around in your schematic by clicking and dragging them. You can delete them by selecting them and pressing the “delete” key. You modify the properties of the elements by selecting them and pressing the “q” key.If you would like to learn more about the Analog Design Environment, select Analog Design Environment->Cadence Analog Design Environment User Guide in the cdnshelp browser window.View WaveformsFrom the Analog Design Environment menu, select Results -> Direct Plot -> Transient Signal. The Waveform Window will then pop up. In the Schematic Window, click on the IN wire and then Click on the OUT wire, then press ESC on your keyboard.The two curves (IN and OUT) will then be displayed in this window:Figure 23 – Waveform ViewerPress the Strip Chart Mode icon (4th icon from right) on the Waveform WindowThe waveforms will then be displayed separately as shown below:Figure 24 – Waveform Viewer, Strip Chart ModeIf you would like to learn more about the Waveform Viewer, select Analog Design Environment->Waveform User Guide in the cdnshelp browser window.Use CalculatorIn Analog Design Environment Window, go to Tools -> Calculator. The Calculator Window will then pop up, as shown below:Figure 25 – CalculatorIn Calculator Window, go to Options -> uncheck RPN. We are going to use the calculator to plot both the current through the capacitor and the absolute value of the capacitor current.In the Calculator Window, click on the tran tab then click the it radio button. In the Schematic Window, click on the lower terminal of the capacitor. Returning to the Calculator Window, the text area at the top should like this:Figure 26 – Calculator after selecting lower capacitor terminalIn the Calculator Window, press the plot icon to plot this waveform in the Waveform Window. In the Calculator Window, select the New Subwindow. In the Calculator Window, press the clear button to erase the text area, select abs, press the “(“ symbol and press the it radio button. In the Schematic Window, click on the lower terminal of the capacitor. Returning to the Calculator Window, press the “)” symbol, the text area at the top should like this:Figure 27 - Calculator after selecting lower capacitor terminalIn the Calculator Window, press the plot button to plot this waveform in the Waveform Window. Your Waveform Window should now look like this:Figure 28 – Waveform Display with current through the capacitor and the absolute value of thecapacitor current。
cadence仿真步骤
CDNLive! Paper – Signal Integrity (SI) for Dual Data Rate (DDR) InterfacePrithi Ramakrishnan iDEN Subscriber Group Plantation, FlPresented atIntroductionThe need for Signal Integrity (SI) analysis for printed circuit board (PCB) design has become essential to ensure first time success of high-speed, high-density digital designs. This paper will cover the usage of Cadence’s Allegro PCB SI tool for the design of a dual data rate (DDR) memory interface in one of Motorola’s products. Specifically, this paper will describe the following key phases of the high-speed design process: Design set-up Pre-route SI analysis Constraint-driven routing Post-route SI analysisDDR interfaces, being source synchronous in nature, feature skew as the fundamental parameter to manage in order to meet setup and hold timing margins. A brief overview of source synchronous signaling and its challenges is also presented to provide context.Project BackgroundThis paper is based on the design of a DDR interface in an iDEN Subscriber Group phone that uses the mobile Linux Java platform. The phone is currently in the final stages of system and factory testing, and is due to be released in the market at the end of August 2007 for Nextel international customers. The phone has a dual-core custom processor with an application processor (ARM 11) and a baseband processor (StarCore) running at 400MHz and 208MHz respectively. The processor has a NAND and DDR controller, both supporting 16-bit interfaces. The memory device used is a multi-chip package (MCP) with stacked NAND (512Mb) and DDR (512Mb) parts. The NAND device is run at 22MHz and the DDR at 133MHz. The interface had to be supported over several memory vendors, and consequently had to account for the difference in timing margins, input capacitances, and buffer drive strengths between different dies and packages. As customer preference for smaller and thinner phones grows, the design and placement of critical components and modules has become more challenging. In addition to incorporating various sections such as Radio Frequency (RF), Power Management, DC, Audio, Digital ICs, and sub-circuits of these modules, design engineers must simultaneously satisfy the rigid placement requirements for components such as speakers, antennas, displays, and cameras. As such, there are very few options and little flexibility in terms of placement of the components. This problem was further accentuated by the fact that several layers of the 10 layer board (3-4-3 structure with one ground plane and no power planes) were reserved for power, audio, and other high frequency (RF) nets, leaving engineers with few layers to choose from for digital circuitry.Figure 1. Memory Interface routes With the DDR interface data switching at 266MHz, we had very tight margins — 600ps for data/DQS lines, 280ps for the address lines, and 180ps for control lines. However, with the NAND interface we had larger margins that were on the order of a few tens of nanoseconds. In these situations, choosing a higher drive strength and using terminators of appropriate values (to meet rise times and avoid overshoot/undershoot) has become a common practice in DDR designs. However, due to the lack of space on the board, we were not in a position to use terminators. Therefore, we used programmable buffers on our processor, and with the help of Cadence SI tools were able to fine-tune the design. Our group migrated from using Mentor Graphics to Cadence SI during this project. As one might expect, this made the task of designing a high speed DDR interface even more challenging. To help overcome this, we worked extensively with Cadence Services, where Ken Willis supported us on the SI portion of the design.The Source Synchronous Design ChallengeBefore discussing the specifics of the Motorola DDR interface, a brief overview of source synchronous signaling is provided here for context. Historically, digital interfaces have utilized “common clock” signaling, as shown in the figure below.Clock DriverTcoInterconnect Delay D0 D1 D2 D0 D1 D2DriveReceiveFigure 2. Common clock designWith common clock interfaces, the clock signal is provided to the driving and receiving components from an external component. The magnitude of the driver’s Tco (time from clock to output valid) and the interconnect delay between the driving and receiving components becomes a limiting factor in the timing of the interface. From a practical standpoint, it becomes increasingly challenging to implement interfaces of this type above several hundred megahertz. In order to accommodate requirements for faster data rates, source synchronous signaling emerged as the new paradigm. This is illustrated in the figure below.StrobeD 0 D 1D 0 D 1DriveReceiveFigure 3. Source synchronous design.In a source synchronous interface, the “clock” is provided locally by the driving component, and is generally called a “strobe” signal. The relationship between the strobe and its associated data bits is known as it leaves the driving component, with setup and hold margins pre-established as the signals are put onto the bus.TsetupTholdFigure 4. Timing diagram. This essentially takes the driver’s Tco as well as the magnitude of the interconnect delay between the driving and receiving chip out of the timing equation altogether. The timing challenge then becomes to manage the skew between the data and strobe signals such that the setup and hold requirements at the receiving end are still met.Technical ApproachThe general technical approach used in this project can be broken down into the following key phases of the high-speed design process: Design set-up Pre-route SI analysis Constraint-driven routing Post-route SI analysisFirst the PCB design database is set up to enable analysis with Allegro PCB SI. Before routing is performed, initial trade-offs are examined at the placement stage, and constraints are captured to facilitate constraint-driven routing. When routing is completed, detailed analysis is performed, interconnect delays extracted, and setup/hold margins are computed. Any adjustments required are fed back to the layout designer, and the postroute analysis is repeated. This basic process is diagrammed below.Design Setup SI Models Pre-Route AnalysisStartConstraints RoutingPost-Route AnalysisnoMargins OK?yes EndFigure 5. SI design process flow. Detail on the major design phases are provided in the subsequent sections. Design Setup By virtue of its direct integration with the Allegro PCB layout database, Allegro SI analysis requires that the design be set up to facilitate the automated extraction, circuit building, netlisting, simulation, and analysis that it performs. This essentially means adding the needed intelligence to the physical Allegro database that allows the tool to do its job. This setup involves the following: Cross section DC nets Device definitions SI models By definition, SI analysis involves the modeling of interconnect parasitics. In order to do this accurately, the tool needs to know the properties and characteristics of the materials used in the PCB stack-up. This information is defined in the Cross Section form, as shown below.It is crucial to get this data correct, as it will be fed to the 2D field solver to model interconnect parasitics during the extraction process. The best source for this detailed information is generally from the PCB fabricator. Layer thickness, dielectric constant, and loss tangent are all critical parameters for the cross section definition. In order for circuit extraction to be done properly, the tool needs to know about DC nets in the design, and what their associated voltage levels are. This accomplishes two main things in the setup; a) enables voltage sources to be injected properly in the extracted circuits, and b) avoids having the tool needlessly trying to extract extremely large DC nets, and hanging up the analysis process. Take the example of a parallel resistor termination. Allegro SI will encounter the resistor as it walks the signal net to be extracted. The tool will look up the SI model assigned to this resistor, splice in the resistor subcircuit, and continue extracting whatever is on the other side of the resistor. If this is a large DC net (ex. VTT), the desire is for the tool to put a voltage source at the 2nd resistor pin, complete the circuit, and simulate the signal. To do this properly, the tool relies on a VOLTAGE property to exist on the DC net, with a numeric value defined. In the absence of the VOLTAGE property, the tool will simply continue to extract, which in the case of a 2000 pin ground net, would be a large waste of computational time. To identify DC nets, clicking “Logic > Identify DC Nets” will spawn the following form.All DC nets in the design should be identified, to fully optimize SI analysis. These can be identified up front in the schematic, as well as in the physical layout as shown here. The next step in the design set-up process is to verify that the logical “CLASS” and “PINUSE” attributes for the devices in the design are defined appropriately. These attributes originate from the schematic symbol libraries and are passed into the Allegro physical layout environment. In an ideal methodology, these libraries would be defined properly and would require no edits. However, this is not always the case, and as these attributes have a bearing on the behavior of the SI analysis, it is worth mention here. The “CLASS” attribute is used to distinguish between different types of components in the PCB design. Legal values of “CLASS” are listed below: IC – This is used for digital integrated circuits, which contain drivers and/or receivers. These types of components are modeled with an SI model of the type “IbisDevice”. When the automated circuit building algorithms in Allegro PCB SI encounter a model of this type, it looks up the buffer model (driver, receiver, or bidirectional) assigned to the pin in question, and inserts it into the circuit along with its associated package parasitics. IO – A component with CLASS = IO is intended for components that connect off-card to other physical layout designs, such as connectors. These components can be associated with a “DesignLink”, which provides netlisting to other physical designs and enables multi-board SI analysis. So circuit building algorithms expect to jump from a device of CLASS=IO to a similar device on a different physical layout. DISCRETE – For devices of this class, circuit building algorithms expect to traverse “through” the component, from one pin to another, inserting a subcircuit in-between. A good example of this would be a series resistor.If CLASS attributes are not set up properly in the source schematic libraries, they can be edited in the physical layout database for analysis by using the form shown below, launched from the “Logic > Parts List” menu pick.The “PINUSE” attribute also impacts the behavior of the SI analysis, as the tool uses this information to determine if a pin is a driver, receiver, bidirectional, or passive pin. As with the “CLASS” attribute, in an ideal methodology this is defined properly in the schematic libraries, and no editing is required in physical layout. “PINUSE” can be modified in two main ways for SI purposes. The most straightforward way is to ensure that the IOCell models used in the IbisDevice models assigned to components have the appropriate Model Type for the signals they are associated to. When SI models are assigned to components, the tool will check for conflicts between the model and the PINUSE it finds for the component in the design, and will use the SI model to automatically override the PINUSE found in the drawing. So if the correct pin types are found in the SI models, the layout will automatically inherit those settings. For components not explicitly modeled, their PINUSE can be set using the form shown below, launched from the “Logic > Pin Type” menu pick.Signal Integrity (SI) models can be assigned using the “Signal Model Assignment” form, shown below.Upon clicking “OK” the selected models will be assigned to the components and saved directly in the layout database. As mentioned previously, “PINUSE” attributes will be synced up, with the SI models superseding attributes in the original layout drawing.Pre-Route SI AnalysisPerforming pre-route analysis is a key part of the high-speed design process. Once critical component placement has been done, Manhattan distances can be used to estimate trace lengths, and can provide a realistic picture of how routed interconnect will potentially perform.Before simulations are run for critical signals, the timing of the interface must be well understood. To accomplish this, we will first sketch timing diagrams for each signal group and then extract a representative signal for analysis. Next, we will explore Z0, layer assignments, drive strength, route lengths, spacing, and terminations for these nets.To sketch the timing diagrams, we first analyze the memory interface. The memory interface consists of both DDR and NAND signals and has around seventy nets. To simplify the analysis of the interface, we first divide these nets based on function and then simulate one net from each group. Accordingly, we select one signal from each of the following groups —clock_ddr, strobe_ddr , data_ddr, control_ddr, address_ddr, control_nand, and data_nand — for our pre-route simulations.To understand the timing relations in the interface, we should look at the following operations between the memory device and the processor — read, write, address write, and control operations. Next, we identify the nets involved and the clocking reference signal for each of these operations. We then calculate the worst case slack available from the setup and hold numbers available in the data sheets. In particular, we adopted the worst case numbers across four different memory vendors, to ensure robustness of the manfactured system in the field..1.ReadDuring the read operation, the memory drives the data and DQS lines. The processor has a delay line (a series of buffers which can be tapped at different points), which is used to delay the DQS signal so that it samples the data at quarter of the cycle. The processor also offers programming options that allow us to apply an offset to the quarter cycle, enabling us to meet our setup and hold times. Hence, the processor self-corrects forstrobe/data skew using this delay line. The granularity of this delay line is 30 ps; that is, each of the buffers of the delay line contributes 30 ps of delay. The data lines 0-7 are clocked with respect to the DQS0 strobe signal, and the data lines 8-15 are clocked with respect to DQS1. Data and strobe lines should be clustered, with the matching constraints determined by the write cycle.2.WriteFigure 7. Write operation at memory interface.During the write operation, both data and DQS are driven by the processor. Data is latched at both the positive and the negative edges of the DQS signals. Here again, data bits 0-7 are clocked by DQS0 and data bits 8-15 are clocked by DQS1. The setup and hold times available as these signals come out of the DDR controller are 1.58ns and 1.7ns respectively and the corresponding times required at the memory to ensure correct operation is 0.9ns. Hence, the slack available for routing is the lesser of 1.58ns – 0.9ns or 1.7ns – 0.9ns, which comes out to be 0.68ns. This amounts to an allowable ~85mm mismatch between the data lines. In addition, we need to make sure that length of the DQS lines is around the average of all the data lines. The data mask signals DQM0 and DQM1 also come into play during the write operation and we should group them along with the respective data lines.3.Address busFigure 8. Address bus operation at memory interface.Both address and clock lines are driven by the processor. The address bits 0-12 are clocked by the differential clock and latched at the positive edge of the clock. The setup and hold times available for these signals from the DDR controller are 1.78ns and 4.22ns respectively and the corresponding times required at the memory to ensure correct operation is 1.5ns for both. Hence the worst case slack for routing is 0.28ns and we have to try to match our signals to meet these numbers. The 0.28ns slack amounts to ~14mm mismatch between the address lines and the clock.4.Control linesFigure 9. Control lines at memory interface.The control signals are clocked by the differential clock and latched at the positive edge of the clock. The setup and hold times coming out of the DDR controller are 1.64ns and 4.04ns respectively. The setup and hold times required at the memory to ensure correct operation is 1.5ns. Hence, the worst case slack for routing is 0.14ns and we have to try and match our signals to meet these numbers. The 0.14 ns slack amounts to ~7mm mismatch between the control lines and the clock.In addition, CLK to DQS skew is around 600 ps. With regards to the NAND lines, setup and hold numbers are in the order of tens of ns and hence routing them as short as possible based on their Manhattan lengths would suffice.To complete pre-route analysis, SigXplorer must be setup for these tasks:a. Extract a topology file for single net analysis. To bring up the net in SigXplorer, it is essential that the models are assigned, as described in Section 2, to each of the drivers, receivers, and components in the signal path.b. Set up parameters for extraction and simulate using SigXplorer.c. Perform measurements using SigWaveThe following screenshots of SigXplorer show this process in detail.Figure 10. SigXplorer screenshots.Since at this point none of the nets in the design are routed we need to set the percent Manhattan section for unrouted interconnect models. We should then select the net, as shown in the next screenshot, for analysis.Analyze Æ SI/EMI Sim Æ PreferencesThe speed at which the signal travels in the trace, where C is 3 x 108 m/s and E reff is the effective dielectric constant seen in the interconnectSets the default lengthfor unrouted transmission linesAt this point, it is important to check if your driver and receiver pins are set correctly. The net chosen in the above example is a data net, it is bi-directional, hence it can be driven both by the memory device as well as the processor. The view topology icon can be clicked to export this net in SigXplorer.The tool extracts the net along with drivers, receivers and strip lines on various layers of the board. Before you start the simulation, you must set the stimulus frequency, pulse step offset, and cycle count. This can be set in the following GUI.Analyze Æ PreferencesBoth the memory device and the processor have programmable drive strengths. The buffer model can bechanged to pick up the various drive strengths that are available in the dml models of the devices till we observe satisfactory waveforms in SigWave.Analyze Æ SI/EMI Sim Æprobeinvokes SigXplorerMake sure you check you driver and load pinsSigXplorer allows you to sweep any of the parameters such as the thickness, length, drive strengths and displays corresponding settle/switch delays, monotonicity, and glitch tolerance for the corresponding simulation. It also allows adding components such as resistors and capacitors and let’s us sweep their values. We added a resistor in series with our clock in or to get rid of ringing in the rising edge. The tool let us determine what values were suitable for this resistor. As shown in the next figure the waveform corresponding to our simulation can bebrought up on SigWave.driverreceiverYou can observe the rise/fall times, look for noise margins, overshoot/undershoot of the receiver waveform. The constraints we develop in the pre-route simulation will be used by the routing tool to ensure correct first time results. This leads to our next section; Constraint-driven routing.Constraint-driven routingOnce pre-route analysis has been done, and trade-offs have been examined, signal wiring constraints need to be developed to drive the constraint-driven routing process. With the DDR interface being point-to-point between the processor and memory, we translated our timing requirements into length constraints to make the routing as straightforward as possible. We also assigned layer constraints for our DDR signals. Both the length and the layer constraints can be directly applied to the constraint manager before the routing process starts.For our particular design, we determined the following layer assignments from the results of the pre-route simulations, taking into account the layer’s characteristic impedance per our stack-up:Layer 6 Æ ground planeLayer 7 Æ clock, add, ctrlLayer 8 Æ data, strobeLayer 9 Æ NAND interfaceBefore we set up our design for auto-routing, we routed the differential clock lines manually on the layers closest to the ground plane. For the rest of the nets, the layer constraints can be created as shown in the following snapshots of the constraint manager.Electrical Constraint Set Æ WiringRight click on board Æ Create new constraintName the constraint (ex. ECSET1)We choose one layer with horizontal orientation and one with vertical for each of our layer sets. You can form groups from the available layer sets and create a new constraint. This constraint, which we define as ECSET1, can be easily read back in the constraint manager and applied to the relevant net group, as shown in the following snapshot.We determined from pre-route analysis the slack available for each of our net groups; however, before we translate these into length constraints it is important to get a report of the Manhattan lengths of each of these signals. To illustrate this, we will focus on the address signals. The Manhattan report of the address lines showed that the shortest lines were 6mm and the longest were 17mm. Accordingly, the minimum length constraint must be longer than 6mm and the maximum length constraint must be longer than 17mm. Additionally, from our timing diagrams, we determined that the maximum spread can be no more than 14mm. Following these restrictions, we set the minimum and maximum length limits for the address line are 11.99 mmto 18.99 mm (shown in the constraint editor window below). Based on the layout designer's recommendations, we were able to constrain a bit tighter (7mm margin) and produce better margins.To enter the length constraint, we open the Net Æ Routing ÆTotal etch length section of the constrain manager. We followed this procedure for all the other net groups. The snapshot that follows shows length constraints associated with the address lines. Here, the key is to not to over-constrain your design, but at the same time have enough constraints so the timing and signal integrity parameters are met. Over-constraining the design severely inhibits the auto-router and may leave large portions of the design (as much as 90%) un-routed.Post-Route SI AnalysisOnce the design is fully routed, detailed simulations can be run for post-route verification. The goal at this phase is to determine final margins over all corners, and find and correct any SI or timing-related issues before the board is released for fabrication. Before starting simulation, it is important to verify that the design is properly routed and that it meets the specifications/constraints. In particular, it is essential to verify that the design does not include dangling and partially-routed/un-routed nets. We must also verify that all the nets meet the length constraints assigned to them. The Constraint Manager window helps identify nets that are in violation (shown in red) and nets that are in compliance (in green). For convenience and clarity, the Constraint Manager also reports the actual route length and the Manhattan lengths for each net.The next step is to bring up the physical layout and visually inspect the nets to ensure that each net is routed in its appropriate layer, or run DRCs if the signals were explicitly limited to specific layers in Physical Constraint Sets. When test points are associated with a net, we must manually verify that the points are in line with the nets (and are not stubs hanging off the nets). Note that when using the simpler Total_Etch_Length constraint, the auto-router can meet routing length constraints for the net, even when there are stubs in the design. These stubs can produce undesirable effects such as reflections and hence this step is important. If there are too manycritical signals to check manually on larger designs, this check can be automated by using an explicit topology and stub length constraints. After manual inspection, we begin post–route simulation and generate reports to analyze the design. We then export the reports to an Excel spreadsheet to facilitate analysis.We generated both delay and reflection reports. The delay report provides information on timing parameters such as propagation delay, switch and settle rise and fall times. The reflection report presents data on signal integrity parameters such as overshoot, undershoot, noise margin, monotonicity, and glitch. Preparing the design for post-route simulation involves the selection of various options in the SI\EMI Sim preferences list. The following screen display describes this process.In the form above, we set up the frequency of the stimulus and the duty cycle. We also set up V meas as thereference for delay calculations. Choosing the reference as V meas , rather than V IH and V IL , makes analysis much easier and is in accordance with the memory datasheet. We chose V meas as 0.9V which is half of the peak-to-peak voltage swing (1.8V).Now that the design is routed, we need to set the parameters for routed interconnects. Here you can specify the minimum coupling distance for nets for the tool to recognize it as a differential pair. This can be done by invoking Analyze Æ SI ÆPref ÆInterconnect Models.Analyze Æ SI/EMI Sim Æ preferencesThe preceding screenshot shows the option that allows us to select the delay and reflection reports. In this form, we also choose all three simulation modes — fast, typical, and slow — to cover all corner cases. In our experience, running typical mode simulations were not enough to determine final timing margins over process, voltage, and temperature. So, we exported the reports to an Excel spread sheet and analyzed the results. Reflection and delay reports simulate only a primary net and none of its neighbors. As a result, these reports do not take into consideration the parasitics of the power and ground pins.Timing > Control typNote:All timings in ns unless labelled otherwise.Component Timingdriving to MemoryTsetup 1.64Tsetup 1.5Thold 4.04Thold 1.5Skew_max = 1.64 - 1.5 = 140ps between clock and controlSkew_max=0.14Clock/Strobe RelationshipsSdram_Ctrl<6:7> is differential clockInterconnect TimingXNet Drvr Rcvr PropDly SettleRise SettleFall AvgSettleSDRAM_CTRL<6>U800 V2_UU2164 C7_U2160.142029 1.13851 1.20538 1.172XNet Drvr Rcvr PropDly SettleRise SettleFall MinSettle MaxSettle MinSettleSkew MaxSettleSkew MaxSkew MarginSDRAM_CTRL<0>U800U21640.1118 1.191 1.235 1.104 1.2350.0680.0630.0680.072SDRAM_CTRL<10>U800U21640.1254 1.165 1.207SDRAM_CTRL<11>U800U21640.1114 1.141 1.187SDRAM_CTRL<12>U800U21640.1217 1.178 1.221SDRAM_CTRL<13>U800U21640.1067 1.114 1.153SDRAM_CTRL<14>U800U21640.09823 1.104 1.143SDRAM_CTRL<2>U800U21640.1274 1.163 1.205SDRAM_CTRL<3>U800U21640.09163 1.108 1.153SDRAM_CTRL<8>U800U21640.1081 1.137 1.182SDRAM_CTRL<4>U800U21640.06959 1.143 1.247SDRAM_CTRL<5>U800U21640.0862 1.169 1.285The preceding spreadsheet was created with data from delay reports and was used to analyze the control lines with respect to the clock. The clock signal in our design is called SDRAM_CTRL<6>. The sheet also lists the driver (U800, the processor), receiver (U2164, memory device), propagation delay (0.142029 ns), settle rise (1.13851 ns), and settle fall (1.20538 ns) values. The average settle delay (1.172 ns) is calculated by averaging the settle rise and settle fall numbers.The control nets SDRAM<0> to SDRAM_CTRL <14> are listed next to the corresponding drivers, receivers, propagation delays, settle rise and settle fall delays. We then look for the minimum and maximum delays of all the settle rise and settle fall delays. These are listed under maximum settle delay (1.235 ns) and minimum settle delay (1.104 ns) respectively. Using these numbers, we calculate the maximum settle skew (0.063 ns), which is the difference between the maximum settle delay (1.235ns) and the average settle time (1.172 ns) of the clock signal. We also calculate the minimum settle skew (0.063 ns), which is the difference between the minimum settle delay (1.104ns) and the average settle time (1.172 ns) of the clock signal. Subtracting the maximum of these two skews, which in our case is 0.068 ns, from the total skew available (0.140 ns) gives the margin (0.072 ns) for these nets.。
cadence原理图仿真
cadence原理图仿真
在进行Cadence原理图仿真时，我们需要注意以下几点，以确保仿真结果的准确性和可靠性：
1. 确认所使用的元件符合仿真要求，并正确地添加到原理图中。
这包括在仿真库中选择合适的元件模型，并将其与其他元件正确地连接起来。
2. 确认仿真的电源和接地连接正确无误。
确保电源和地线的连接不会导致任何不良影响，如电压下降或噪声干扰。
3. 设置仿真参数，如仿真时间、仿真步长等。
根据所需的仿真精度和仿真效率，选择适当的仿真参数。
4. 进行信号源的设置。
这包括选择合适的信号源类型（如AC
信号、脉冲信号等）、设置信号源的频率和振幅等参数。
5. 添加测量器件，以便在仿真过程中监测所需的电压或电流。
这些测量器件可以是电压表、电流表或示波器等。
6. 设置仿真分析类型。
根据需要进行直流分析、交流分析或者是时域分析等。
选择适当的仿真分析类型以获得所需的结果。
7. 运行仿真并分析结果。
运行仿真过程，等待仿真完成后，通过分析仿真结果来获取我们所需的电压、电流或其他信号参数。
通过遵循以上步骤，我们可以在Cadence中进行原理图仿真，并获取准确可靠的仿真结果，以验证电路设计的正确性和性能。
基于Cadence的信号完整性仿真步骤
目录1.仿真前的准备工作 (2)1.1找到需要仿真的芯片的IBIS模型 (2)1.2模型转换（IBIS→DML） (2)1.3添加模型到Cadence的模型库中 (5)2. 对电路板进行设置（Setup Advisor） (7)2.1准备好要仿真的电路板 (7)2.2调用参数设置向导 (7)2.3叠层设置 (8)2.4设置DC电压值 (9)2.5器件设置（Device Setup） (10)2.6 SI模型分配 (12)2.7 SI检查（SI Audit） (16)2.8完成参数设置 (18)3.进行信号完整性仿真（反射） (19)3.1开始仿真 (19)3.2选择所要仿真的网络 (19)3.3提取网络的拓扑结构 (20)3.4给驱动端U8添加激励信号 (21)3.5设置激励信号的参数 (22)3.6执行反射仿真 (22)3.7仿真结果 (22)1.仿真前的准备工作1.1找到需要仿真的芯片的IBIS模型一般可以从芯片制造商网站上找到，如果没有，可能要通过其它途径获得如从SPICE模型中提取。
1.2模型转换 （IBIS→DML）将IBIS模型转换为DML模型，运用Cadence的Model Integrity工具将IBIS模型转化为Cadence能识别的DML模型，并验证仿真模型。
（1）单击“开始”按钮→“所有程序”→“Allegro SPB 15.5”→“Model Integrity”，如图1-1所示：图1-1 Model Integrity工具窗口（2）选择“File”→“Open”，打开一个IBIS模型如图1-2所示：图1-2 打开一个IBIS模型（3）在“Physical View”栏中，单击IBIS文件“sn74avca16245”→选择菜单栏里的“Options”→“Translation Options Editor”→弹出“Translation Options”窗口，如图1-3所示：图1-3 Translation Options窗口（4）默认选择“Make model names unique”，这个设置为每个IOCell模型名附加IBIS文件名。
Cadence基础仿真分析与电路控制描述
Cadence基础仿真分析与电路控制描述Cadence是一款主要用于集成电路设计和仿真分析的软件工具。
本文档将介绍Cadence的基础仿真分析功能以及电路控制描述的方法。
Cadence基础仿真分析Cadence提供了多种仿真分析工具，包括电路级仿真、时钟级仿真和系统级仿真等。
这些工具可用于验证电路设计的正确性，并进行性能评估。
在进行仿真分析之前，需要进行以下步骤：1. 设计：使用Cadence的设计工具创建电路图和原理图，定义电路的结构和功能。
2. 参数设置：对电路器件进行参数设置，包括电阻、电容、电感等元件的数值设定。
3. 仿真配置：选择适当的仿真工具和仿真设置，如仿真类型、仿真时间和仿真模型等。
接下来，执行仿真分析：1. 电路级仿真：通过电路级仿真工具，如Spectre，对电路进行验证和性能评估。
参数设置和仿真配置完成后，运行仿真并分析仿真结果。
2. 时钟级仿真：通过时钟级仿真工具，如Virtuoso AMS Designer，对电路中时序相关的功能进行验证。
设置时钟源和时钟周期等参数，并运行仿真以验证电路的时序性能。
3. 系统级仿真：通过系统级仿真工具，如Virtuoso System Design Platform，对整个电路系统进行仿真。
设置系统级的参数和信号源，并进行仿真分析。
电路控制描述在Cadence中，可以使用Verilog-A或Verilog-AMS等硬件描述语言来描述电路的行为和控制。
1. Verilog-A：主要用于模拟连续时间的电路。
可以使用Verilog-A描述电路的行为和相互之间的连接关系。
通过编写Verilog-A代码，可以实现电路的仿真和性能分析。
2. Verilog-AMS：结合了连续时间和离散时间的特性，可用于描述混合信号电路。
除了模拟电路行为之外，还可以描述数字电路部分。
通过编写Verilog-AMS代码，可以实现电路的混合仿真和性能分析。
使用这些硬件描述语言时，需要了解其语法和规范，并根据实际需求编写相应的代码。
Cadence-SI-Simulation
Cadence仿真介绍第一部分：仿真流程第二部分：IBIS模型IBIS模型和SPICE模型比较：SPICE模型：（1）电压/电流/时间等关系从器件图形、材料特性得来，建立在低级数据的基础上（2）每个buffer中的器件分别描述/仿真（3）仿真速度很慢（4）包含芯片制造工艺信息IBIS模型：（1）电压/电流/时间关系建立在IV/VT数据曲线上（2）没有包括电路细节（3）仿真速度快，是SPICE模型的25倍以上（4）不包含芯片内部制造工艺信息基于上述原因，对于在系统级的设计，我们更倾向于使用IBIS模型。
目前IBIS主要使用的有V1.1，V2.1，V3.2及V4.0等版本。
模型结构如下图：C_pkg，R_pkg，L_pkg为封装参数；C_comp为晶片pad电容；Power_Clamp，GND_Clamp 为ESD结构的V/I曲线。
输出模型比输入模型多一个pull-up，pull-down的V/T曲线。
Cadence的model integrity工具负责对IBIS模型进行语法检查、编辑以及进行DML格式转换。
Cadence仿真不直接使用IBIS模型，而必须先把IBIS转换成DML。
<实例操作演示>第三部分：电路板设置电路板设置包括：（1）叠层设置；（2）DC电压设置；（3）器件设置；（4）模型分配；上述步骤可以通过setup advisor向导设置。
1，叠层设置2，DC电压设置3，器件设置4，模型分配电阻、电容、电感等无源器件的模型可以通过建立ESPICE模型来获得。
<实例操作演示>第四部分：设置仿真参数模型分配完成后，就可以进行仿真了。
在进行仿真之前，需要对仿真的参数进行设置。
Pulse cycle count：通过指定系统传输的脉冲数目来确定仿真的持续时间。
Pulse Clock Frequency：确定仿真中用来激励驱动器的脉冲电压源的频率。
Pulse Duty cycle：脉冲占空比。
基于Cadence的电源完整性仿真步骤
基于Cadence的电源完整性仿真步骤1、设置电路板的参数用PI模式打开要仿真的电路板，仿真其CPU_1.8V电源平面的完整性。
1.1调用设置向导在PI中选择“Analyze”—>“Power Integrity”出现提示对话框，点击“确定”后出现设置向导窗口。
1.2板框（Board Outline）点击“Next”进入设置向导里的“Board Outline”窗口PI需要一个板框来进行布局和电源平面提取。
如果板框不完整或不存在，则上图右上角会有信息提示。
1.3Stack-up设置点击“Next”进入设置向导里的“Stack-up”窗口。
PI需要叠层关系来计算电源对从而为平面建模。
如果叠层不存在或者不包含平面层，则屏幕右上角会有信息显示。
在这里可以调整叠层关系（Edit stack-up）或从另一个设计中导入（Import stack-up）。
屏幕右上角有相应的示意图，如图：当不勾选“Physical view”时，各层厚度平均显示；勾选后各层按比例显示。
1.4DC Net-Plane Association点击“Next”进入设置向导里的“DC Net-Plane Association”窗口，如图：PI 在估算去耦电容之前需要给每一个需要仿真的电源平面分配DC电压，在这里可以调整现有的电压分配。
同一层的分割平面会有不同的“shape”，因此每个“shape”都有一个不同的DC网络。
1.5DC Power Pair Setup点击“Next”进入设置向导里的“DC Power Pair Setup”窗口，如图：在进行PI 之前，电源和地平面必须成对。
一个地可以被多个平面共享，但一次只能分析一对平面。
在“Plane 1”栏中选择要分析的平面，在“Plane 2”栏中选择对应的平面，选中的平面对将在右边的叠层视图中高亮。
点击“Add”创建对应的平面对。
1.6选择去耦电容点击“Next”，如图：1.7选择电容模型点击“Next”，如图：选好所用的电容模型后，点击“Finish”完成对电路板参数的设置，弹出“Power Integrity Design&Analyze”窗口，如图：2、单节点仿真可以通过运行单节点仿真来验证选择的电容数量能否在频率范围内维持目标阻抗。
CADENCE仿真步骤
CADENCE仿真步骤1.电路设计：首先，需要使用电路设计软件（例如OrCAD）绘制电路原理图。
在设计电路时，应该合理选择电路元件，确保其参数和规格满足设计要求。
2.创建电路网络：在CADENCE中创建电路网络是第一步。
通过将电路原理图导入到CADENCE中，可以建立电路的模型。
在建立电路网络时，应定义元件的参数值，并将其连接起来。
3.定义仿真设置：在进行仿真之前，需要设置仿真参数。
这些参数包括仿真类型（例如直流、交流、蒙特卡罗等）、仿真步长、仿真时间等。
此外，还可以设置其他参数，如故障分析、参数扫描等。
4. 运行仿真：设置好仿真参数后，可以开始运行仿真了。
CADENCE 提供了多种仿真工具，如PSpice、Spectre等，可以根据不同的需求选择适合的工具。
在仿真过程中，CADENCE会使用电路元件的模型计算电路参数，根据仿真设置提供的信息生成相应的结果。
5.分析仿真结果：一旦仿真完成，CADENCE会生成仿真结果文件。
通过分析仿真结果，可以评估电路设计的性能。
常见的仿真结果包括电流、电压、功耗、频率响应等。
可以将仿真结果与预期结果进行比较，找出设计中的问题并进行优化。
6.优化电路设计：根据仿真结果，可以对电路设计进行调整和优化。
优化可以包括选择不同的元件、调整元件参数、改变电路拓扑等。
通过不断迭代仿真和优化，可以逐步改进电路设计，使其达到预期的性能指标。
7.验证仿真结果：当设计经过一系列的优化后，需要验证仿真结果是否可靠。
一种常用的验证方法是进行物理验证，即将最终的电路设计制作出来并测量其实际性能。
通过比较实际测量结果与仿真结果，可以验证仿真的准确性，并进行必要的修正。
8. 导出设计文件：一旦电路设计完成并验证通过，就可以将设计文件导出，准备进一步的生产制造。
将设计文件导出为标准的格式（如Gerber文件），可以将其发送给制造商进行生产。
总结：CADENCE仿真步骤包括电路设计、创建电路网络、定义仿真设置、运行仿真、分析仿真结果、优化电路设计、验证仿真结果和导出设计文件。
cadence使用教程
cadence使用教程Cadence是一种电路设计和仿真软件，非常适合电子工程师用于电路设计和分析。
在本教程中，我们将介绍如何使用Cadence进行基本的电路设计和仿真。
首先，打开Cadence软件，并新建一个新项目。
请确保你已经安装了Cadence软件，并且拥有一个有效的许可证。
在新项目中，你需要定义电路的基本参数，如电源电压、电阻值等。
可以通过绘制原理图的方式来完成这些参数的定义。
在绘图界面中，你可以选择不同的元件，包括电源、电阻、电容、电感等。
你可以使用菜单栏中的工具来放置和连接这些元件。
一旦电路图绘制完成，你可以对电路进行仿真。
首先，需要选择合适的仿真器。
Cadence提供了多种仿真器，如Spectre和HSPICE。
选择一个适合你电路的仿真器，并设置仿真参数，如仿真时间、仿真步长等。
在仿真之前，你首先需要对电路进行布局。
布局涉及将电路中的元件放置在芯片上，并根据布线规则进行连接。
Cadence提供了强大的布局工具，可以帮助你完成这个过程。
完成布局后，你可以进行后仿真。
后仿真涉及将布局好的电路导入到仿真器中，并进行仿真分析。
你可以查看电路的性能指标，如电压、电流和功耗等。
除了基本的电路设计和仿真，Cadence还提供了其他功能，如噪声分析、温度分析和优化设计等。
你可以根据需要选择适合的功能。
总的来说，Cadence是一个功能强大的电路设计和仿真软件。
通过本教程，你可以学会如何使用Cadence进行基本的电路设计和仿真。
希望这对你的电子工程项目有所帮助。
CADENCE仿真步骤
Cadence SPECCTRAQuest 仿真步骤[摘要]本文介绍了Cadence SPECCTRAQuest在高速数字电路的PCB设计中采用的基于信号完整性分析的设计方法的全过程。
从信号完整性仿真前的环境参数的设置，到对所有的高速数字信号赋予PCB板级的信号传输模型，再到通过对信号完整性的计算分析找到设计的解空间，这就是高速数字电路PCB板级设计的基础。
[关键词]板级电路仿真 I/O Buffer Information Specification（IBIS）1 引言电路板级仿真对于今天大多数的PCB板级设计而言已不再是一种选择而是必然之路。
在相当长的一段时间，由于PCB仿真软件使用复杂、缺乏必需的仿真模型、PCB仿真软件成本偏高等原因导致仿真在电路板级设计中没有得到普及。
随着集成电路的工作速度不断提高，电路的复杂性不断增加之后，多层板和高密度电路板的出现等等都对PCB板级设计提出了更新更高的要求。
尤其是半导体技术的飞速发展，数字器件复杂度越来越高，门电路的规模达到成千上万甚至上百万，现在一个芯片可以完成过去整个电路板的功能，从而使相同的PCB 上可以容纳更多的功能。
PCB已不仅仅是支撑电子元器件的平台，而变成了一个高性能的系统结构。
这样，信号完整性在PCB板级设计中成为了一个必须考虑的一个问题。
传统的PCB板的设计依次经过电路设计、版图设计、PCB制作等工序，而PCB的性能只有通过一系列仪器测试电路板原型来评定。
如果不能满足性能的要求，上述的过程就需要经过多次的重复，尤其是有些问题往往很难将其量化，反复多次就不可避免。
这些在当前激烈的市场竞争面前，无论是设计时间、设计的成本还是设计的复杂程度上都无法满足要求。
在现在的PCB板级设计中采用电路板级仿真已经成为必然。
基于信号完整性的PCB仿真设计就是根据完整的仿真模型通过对信号完整性的计算分析得出设计的解空间，然后在此基础上完成PCB设计，最后对设计进行验证是否满足预计的信号完整性要求。
CADENCE 仿真流程
第一章进行SI仿真得PCB板图得准备仿真前得准备工作主要包括以下几点:1、仿真板得准备●原理图设计;●PCB封装设计;●PCB板外型边框(Outline)设计,PCB板禁止布线区划分(Keepouts);●输出网表(如果就是用CADENCE得Concept HDL设计得原理图,可将网表直接Expot 到BRD文件中;如果就是用PowerPCB设计得板图,转换到allegro中得板图,其操作见附录一得说明);●器件预布局(Placement):将其中得关键器件进行合理得预布局,主要涉及相对距离、抗干扰、散热、高频电路与低频电路、数字电路与模拟电路等方面;●PCB板布线分区(Rooms):主要用来区分高频电路与低频电路、数字电路与模拟电路以及相对独立得电路。
元器件得布局以及电源与地线得处理将直接影响到电路性能与电磁兼容性能;2、器件模型得准备●收集器件得IBIS模型(网上下载、向代理申请、修改同类型器件得IBIS模型等)●收集器件得关键参数,如Tco、Tsetup、Tholdup等及系统有关得时间参数Tclock、Tskew、Tjitter●对IBIS模型进行整理、检查、纠错与验证。
3、确定需要仿真得电路部分,一般包括频率较高,负载较多,拓扑结构比较复杂(点到多点、多点到多点),时钟电路等关键信号线第二章IBIS模型得转化与加载CADENCE中得信号完整性仿真就是建立在IBIS模型得基础上得,但又不就是直接应用IBIS模型,CADECE得软件自带一个将IBIS模型转换为自己可用得DML(Device Model Library)模型得功能模块,本章主要就IBIS模型得转换及加载进行讲解。
1、IBIS模型到DML模型得转换在Allegro窗口中选择Analyse\SI/EMI SIM\Library,打开“signal analyze library browser”窗口,在该窗口得右下方点击“Translate →”按钮,在出现得下拉菜单中选择“ibis2signois”项,出现“Select IBIS Source File”窗口(图1),选择想要进行转换得源IBIS文件,按下“打开”按钮,出现转换后文件名及路径设置窗口(缺省设置为与源IBIS文件同名并同路径放置,但此处文件名后缀为dml),设置后按下“保存”按钮,出现保存确定窗口(图2),点击OK按钮即可,随后会出现一个“messages”窗口,该窗口中得报告文件说明在模型转换过程中出现得问题,对其中得“warning”可不用在意,但如果出现“error”则必须进行修改后重新进行模型格式转化直到没有“error”出现为止,此时转换得到得dml文件才就是有效得。
cadence对pcb进行后仿真
一、一般流程1、IBIS库转换层DML格式2、给器件加载模型并定义管脚3、定义电源、地网络等4、提取拓扑结构5、设置仿真参数6、仿真结果分析具体步骤请参见一些cadence后仿真的相关pdf文档。
二、补充说明在加载模型之后注意定义管脚，如果没有定义，仿真结果会有很大差异。
方法如下：1、在上图给器件加载模型的窗口中，点击fild model 为器件加载模型，然后点击edit model，出现下图：2、选择assign signal pins 然后在all pin中选择需要定义的管脚。
被选择的管脚会出现在selected pin方框中。
点击右侧的browse 出现下图：3、在dml model browser中选择需要的Iocell 关闭窗口、确定、完成。
4、如需对差分信号进行仿真的话，需要对差分pin进行设置。
三、pcb中FPGA与DDR2之间一根数据线的仿真。
1、提取的信号线为下图中白色高亮。
1、提取的拓扑结构包括走线和过孔的一些具体信息。
U17是DDR2，FPGA1是xilinx—c6v130tff784 2、层叠结构所仿真的信号线走的是S1层，为达到50 ohm 匹配，s1上下介质厚度为6mil。
3、仿真参数4、仿真结果Ddr2发送fpga接收时候的波形：浅绿色和浅蓝色分别是ddr2的pin和pad处的波形。
黑色和蓝色分别是fpga的pin和pad处的波形。
Fpga发送，ddr2接收时候的波形：5、以下是将走线拉直以后的仿真结果：Ddr2 发送，fpga接收：Fpga发送。
Ddr2接收：新手第一次做的仿真，希望与大家一起交流讨论。
可以加Q： 5.1.9.7.3.1.9.8.。
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第一章在Allegro 中准备好进行SI 仿真的PCB 板图1)在Cadence 中进行SI 分析可以通过几种方式得到结果：* Allegro 的PCB 画板界面，通过处理可以直接得到结果，或者直接以*.brd 存盘。
* 使用SpecctreQuest 打开*.brd，进行必要设置，通过处理直接得到结果。
这实际与上述方式类似，只不过是两个独立的模块，真正的仿真软件是下面的SigXplore 程序。
* 直接打开SigXplore 建立拓扑进行仿真。
2)从PowerPCB 转换到Allegro 格式在PowerPCb 中对已经完成的PCB 板，作如下操作：在文件菜单，选择Export 操作，出现File Export 窗口，选择ASCII 格式*.asc 文件格式，并指定文件名称和路径(图1.1)。
图1.1 在PowerPCB 中输出通用ASC 格式文件图1.2 PowerPCB 导出格式设置窗口点击图1.1 的保存按钮后出现图1.2 ASCII 输出定制窗口，在该窗口中，点击“Select All”项、在Expand Attributes 中选中Parts 和Nets 两项，尤其注意在Format 窗口只能选择PowerPCB V3.0 以下版本格式，否则Allegro 不能正确导入。
3)在Allegro 中导入*.ascPCB 板图在文件菜单，选择Import 操作，出现一个下拉菜单，在下拉菜单中选择PADS 项，出现PADS IN 设置窗口(图1.3)，在该窗口中需要设置3 个必要参数：图1.3 转换阿三次文件参数设置窗口i. 在的一栏那填入源asc 文件的目录ii. 在第二栏指定转换必须的pads_in.ini 文件所在目录(也可将此文件拷入工作目录中，此例)iii. 指定转换后的文件存放目录然后运行“Run”，将在指定的目录中生成转换成功的.brd 文件。
注：pads_in.ini 所在目录路：.\Psd_14.2\Tools\PCB\bin 中。
4)在Allegro 文件菜单中使用打开功能将转换好的PCB 板调入Allegro 中。
第二章转换IBIS 库到dml 格式并加载1)库转换操作过程在Allegro 菜单中选择Analyze \ SI/EMI SIM \Library 选项，打开“Signal Analyze Library Browser”窗口，在该窗口的右下方点击“Translatr ->”按钮，在出现的下拉菜单中选择“ibis2signois”项，出现“Select IBIS Source File”窗口(图2.1).按下“打开”按钮，随后出现转换后文件存放目的设置窗口，设置后按下“保存”键，出现保存认定窗口(图2.2)。
注意：必须对此窗口默认的路径设置进行修改，否则无法生成.dml 文件。
图2.1 IBIS 库转换原文件路径设置窗口原该窗口的默认设置为“ibis2signoise in="E:"\_ED\30\82559.ibs out="82559".dml”，实际上ibis2signoise 是一个DOS 文件，可能在一些场合，可执行文件后面的命令参数中“in=”和“out=”被认为是非法字符，所以，将它修改为“ibis2signoise E:\_ED\30\82559.ibs ”即可，它将在IBIS 文件所在目录建立同名的dml 文件。
图2.2 IBIS To dml 转换设置路径窗口(需修改)转换完成以后，会有报告文件弹出，在文件中只要没有“Error”提示，转换文件有效。
2)加载转换后的dml 库图2.3 Signal Analyze Library Browser 窗口在Signal Analyze Library Browser 窗口(图2.3),加载转换后的dml 库文件。
首先点击“Add Existing Library ->”按钮，出现下来菜单(图2.4)，该菜单有四个选项：1. Local Lib: 直接指定一个确定的库文件。
这些库文件在：…Psd_14.2\share\pcb \signal \SignalPartLib 中。
图2.4 加载库文件的几个方法2. Local Library Path :指定一个人目录并将目录中所有库文件调入。
在…Psd_14.2\share \pcb \signal\SignalPartLib 中安装时，内置有三个库文件目录(安装时没有选择附加的仿真用库)：DEFAULT_LIB、Dig_lib(内含abt、als、alvc、fttl 四个子目录)、Packages。
其中als 子目录中有X4ALS 系列标注逻辑器件库，如74als162 等。
3. Standard Cadence Library：在加载两个索引文件(\Psd_14.2\share\pcb\signal)：cds_models.ndx和cds_partlib.ndx，前者包括模块信息，后者包括仿真器件信息。
3)加载成功以后可以点击set working 按钮，将其设置为工作库。
第三章给器件加载对应模型1) 给器件加载模型在Allegro 菜单中选择Analyze \ SI/EMI SIM \Model 选项，打开“Signal Model Assignmen”窗口(图3.1)。
图3.1 为器件指定模型窗口在图3.1 中显示所有使用到的器件名称，选中一个准备设置模型的器件并点击Find 按钮，出现，Model Browser 窗口(图3.2)。
在Model Name Pattern 窗口中填入“*”号，一些模型的名称进入下面的列表框，图3.2 浏览模型窗口在列表框里点击你需要的模块后，在图3.1 中U1(和U2)的“Signal Name”列里就会出现它的模型名称。
2)器件、元件的建模如果在图3.1 里准备加载的模型是无源器件或者是需要自己临时创建的模型，则点击在图3.1 中的create model 按钮出现图3.2 创建模型窗口，对于电阻电容选择Espicemodel(选中蓝色箭头所指项目)后将出现,Creat ESpick Device Model窗口(图3.3)。
其他有源器件用IBISdevice 模型(选中红色箭头所指项目)，然后按提示输入value 及各管脚的功能即可，同时可以存盘生成*.dat 文件，这样以后进行仿真时直接load 即可。
此时这个新建的模型就出现在所选器件的“模型名称“栏中。
图3.3 无源器件建模窗口无源器件包括电阻。
电容、电感，图中的Common 项是设置该元件是否有公用(接地或电源)管脚。
第四章定义板子的地线、电源电压器件仿真必须设置直流电源，否则仿真不能进行，只有定义了电压的电源和地信号，才能在拓补结构中将电源的信号模型调进来。
此操作在Logic 菜单项中选择Identify Nets..选项，出现Identify DC Nets 窗口(图4.1 分别选中VCC 和GND 网络，在Voltage 栏填入5V 和OV，然后确认，完成设置。
图4.1 直流电源设置窗口调整PCB 板叠层结构满足阻抗要求该功能分别从Aleegro、SpecctraQuest 两个模块进入后进行设置。
1) 从Allegro 主窗口设置在Tools 菜单选择Setaup Advior 选项，出现DatBase Setup Advsor 窗口，直接按下“Next“按钮，出现新的DatBase Setup Advsor –Cross-Section 窗口，其中有个“Edit Cross-Section”按键，按下此键进入叠层设计窗口(图5.1)，在这个类似Excel 表格式地窗口里，输入需要的各种参数，在表地最后一栏直接计算出该层的阻抗值。
图5.1 叠层设置窗口2) 从SpecctraQuest 窗口设置直接从Setup 菜单选择Cross-Section 项进入图5.1 窗口第六章设置仿真参数在正式进行仿真之前，还需要对各参数进行设置，以便使最终结果更加准确的反映设计者的要求。
这个步骤可以在SpecctraQuest 模块里，也可以在Sigxplore 中完成。
具体需要设置的参数根据不同仿真有不同的要求，大致如下：仿真的周期数（measurement cycle）时钟频率（Clock frequency）占空比（duty cycle）偏移量（offset）固定仿真时间（fixed duration）波形取样时间（waveform resolution）截止频率（cutoff frequency）仿真模式（FTS mode）驱动激励（drive excitation）测量模式(measurement mode)1）SpecctraQuest 模块里设置仿真参数在SpecctraQuest 的菜单里选中Analyze\SI/EMI SIM\Prefences，出现参数设置窗口（图6.1）图6.1 仿真参数设置2）在SigXplore 里的选中Analyze\Prefences 进入的参数设置窗口与图6.1 类似。
第七章用探针(Probe)指定仿真信号线1) 建立仿真信号线网表在SpecctraQuest 里的Logic 下拉菜单里，选择create list of nets,出现“CreatList of Net”窗口(图7.1)。
在窗口上边的Net List Name 栏中填入自己起的网络名称，在“Net Filter”栏输入“* ”;在“Available nets”列表栏中选中需要仿真的网络并将其添加到右边“Selected Nets”栏里。
然后将生成的网表文件进行保存。
图7.1 建立仿真网络2) 选择仿真网络选中Analyz\SI/EMI Sim\Probe 命令，在弹出的signal analysis 窗口的net 一栏，敲入*,或者通过list of nets，将网表文件调入。
这样所有的net 都出现在最左边的框里，可以选择任何一个信号线进行模拟。
(图7.2)图7.2 选择仿真网络第八章生成仿真结果报告、设定报告包括的参数选中要进行模拟的信号线之后，点击图7.2 下方Reports 功能键，在弹出analysis report generator窗口里进行不同的参数条件设置，如SSN, Reflection、CrossTalk 等等，参数设置完成之后，点击create report 就可以分别生成对反射，串扰，地弹等等的仿真结果报告。
第九章提取电路拓扑结构（建立）1）通过在Aleegro 和SpecctraQuest 界面提取电路拓扑结构点击图7.2 中View Toplogy，假设没有任何设置错误，将直接进入拓扑界面。