Product Documentation
Voltus-Fi Custom Power Integrity Solution XL User Guide
Product Version IC23.1, August 2023

7

IR Drop Analysis Results

Overview of IR Drop Analysis

Voltus-Fi-XL uses the simulation database generated by Spectre APS/XPS simulators and displays the results of the IR drop analysis on the Virtuoso layout. It also generates text reports of the analyses and lets you query the analyses results to view specific violations in the layout. This is used to debug the high IR drop regions in the design.

Batch mode support is provided for loading IR drop analysis results and generating text reports. The following commands are used to load and print IR drop analysis results in Voltus-Fi-XL:

Signal Net IR Drop Analysis

By default, IR drop analysis can only be applied to power nets, which are nets driven by DC or constant voltage sources. The advanced feature, signal net IR drop analysis, lets you perform IR drop analysis on signal nets, which are nets that are not connected to any DC or constant voltage source.

In the signal net IR drop analysis, the maximum or average IR drop is reported using the analysis=[sigvmax sigvavg] statement in the EMIR control file (emir.config). The signal net IR drop is reported as the difference between the reference voltage and the voltage of the sub node (vref-vnode). For a particular signal net, the reference voltage for calculating the IR drop value at each sub node and time point is defined as the average voltage of all sub nodes (reftype=[avg]), the maximum voltage of all sub nodes (reftype=[max]), or the voltage of a user-specified pin (reftype=[pin]).

Alternatively, for nodes driven by voltage sources and the voltage of the net driven by the voltage source can be used as reference (findsrc=yes).

The following is an example of the EMIR control file (emir.config):

net name=[X1.*] analysis=[sigvmax] reftype=[max] findsrc=yes
solver method=direct

In the above example, the signal net IR drop analysis is performed for all nets X1.*. The maximum IR drop for the sub nodes of each net is reported. For the IR drop analysis at each net and time point, the sub node with the highest voltage is picked as the reference voltage. For any net driven by a vsource, the voltage of the sub node driven by the vsource is used as reference.

When using reftype=[max] for a net with three sub nodes: net1_1 (1V), net1_2 (2V), and net1_3 (3V), the detected reference voltage will be 3V, and the IR drop calculated will be 2V for net1_1, 1V for net1_2, and 0V for net1_3. When using reftype=[avg] the reference voltage will be 2V, and the IR drop calculated will be 1V for net1_1, 0V for net1_2, and -1V for net1_3.

In addition, if net1_2 is driven by a vsource and findsrc has been specified as yes, the voltages of net1_2, at all time points, will be used as the reference voltages.

Power Gate Support in Voltus-Fi-XL

Power networks may contain power gates which enable or disable the power supply in the circuit. These power gates split the power supply RC network into two parts. The RC network driving the power gate, and the RC network being driven by the power gate. This is shown in the figure below. The MMSIM EMIR analysis can handle such power gates.

To invoke the power gating handling, add the power gate setting in the EMIR control file (emir.config), as shown below.

net pwrgate=[vdd vdd_int] analysis=[vavg]

Both, the power supply net (vdd) driving the power gates, and the internal power supply net (vdd_int) driven by the power gates, need to be specified in the net statement in any order. Wildcarding is supported for the internal power supply net(s), but not for the power supply net.

Next, the required analyses need to be defined, as shown above. The IR drop report includes both the power supply net in the usual report filename, for example, input.rpt_ir and the internal power supply net is reported in a file, such as input.rpt_pwg or input.emirtap.rpt_pwg for direct and iterated methods, respectively. As for the EM analyses, they are performed as usual, if specified.

In addition, an important parameter Ton is also be reported in the .rpt_pwg file. It reports the time taken to power up the terminal of the internal power supply net to 95% of the power supply level (VDD).

Note: The parameter Ton can be infinity if the internal power supply level does not reach 95% of VDD.

The subsequent sections cover the various options available in Voltus-Fi-XL for viewing the IR drop analysis results on the Virtuoso layout.

Power-Up Summary Report

Voltus-Fi-XL supports viewing of the power-up test summary report in the GUI. The feature is enabled only after the IR drop analysis results are loaded. For this, the Power-up Report button is provided on the IR tab of the IR/EM Results form.

When clicked, a view-only power-up summary report is displayed in the GUI. The report is available only if the following conditions are met:

A sample power-up report is shown below.

In addition to information about the type of simulation results, the report contains the following information:

Static EMIR Analysis

A static EMIR analysis evaluates IR drop and EM currents based on user-provided subcircuit instance current consumptions without running a transient or DC simulation. The user-provided currents are distributed to the tap devices based on the W/L ratio of the devices in the design. The IR drop and EM current analysis is performed based on the value of current at each tap device.

The static EMIR analysis is enabled with the “static ifile” statement in the EMIR configuration file.

net name=[I1.VDD I1.VSS] analysis=[vavg iavg]
static ifile="static_currents.txt"

Since the analysis is static, the IR drop vmax and vavg, and the EM current imax, irms, and iavg values will be the same, and just one of these can be selected in the statement.

The subckt instance currents are defined (in A) in the “static_currents.txt” file with the subckt instance name, the subckt port name, and the value of current flowing in the port.

I1 VDD 0.001
I1.I2 VDD 0.005
I1.I2/I3 VDD 0.00001
I1.I2/I3/I4 VDD 0.000005
I1 VSS ‐0.005

The accuracy of the static EMIR analysis depends greatly on the detailed current information in the static_ifile. It is highly recommended that you provide the current consumption for each subckt instance.

The results of the static EMIR analysis are written into the same IR drop and EM current text reports, and into the same binary EM database as the dynamic EMIR analysis. Static EMIR analysis cannot be combined with the dynamic analysis. You can perform either a static or a dynamic EMIR analysis at one time. When running the static EMIR analysis all other Spectre analyses like DC, TRAN and so on will be ignored.

The static EMIR analysis can also be applied to designs with power gates. In that case the pwrgate statement needs to be added to the EMIR configuration file as follows:

net name=[I1.VDD] analysis=[vavg iavg]
static ifile="static_currents.txt"
net pwrgate=[I1.VDD I1.VDD_INT] analysis=[vavg iavg]

and the power gate current is required to be added to the “static_currents.txt” file as follows:

I1 VDD 0.001
I1 VDD_INT 0.0005
To support users setting up the static EMIR flow, the static EMIR current file is automatically generated when running a dynamic EMIR analysis (file extension: static).

Static Power Grid Solver

The static power grid solver (SPGS) feature of Spectre can be used in Voltus-Fi-XL to calculate all pin-to-tap resistances based on the description of a DSPF file and the options set in the EMIR configuration file. The resistances calculated by SPGS are electrically equivalent resistances, and not the summation of resistors. The calculation assumes that all pins are connected together to form a global pin. After calculation, the resistance between the global pin and all taps is generated and listed based on the significance of their values.

This feature can also be used to calculate the pin to pin resistance between any two nodes of the same net.

The diagram below shows the definition of pin, sub nodes, and tap nodes in the DSPF file.

The static EMIR analysis is enabled with the “spgs net=...” statement in the EMIR configuration file.

spgs net=[i1.vcc i1.vss]
spgs rshort=1e-12
spgs pwrgate = [i1.vcc i1.outp]

The net statement defines the power nets to be analyzed. Resistors in the power net can be optionally shorted with the rshort option. If the power net contains a power gate, then the pwrgate option needs to be defined in the configuration file.

The SPGS flow requires the DSPF file to be included in the Spectre input file with the dspf_include statement, as shown below.

dspf_include “pll.spf”

The power nets need to be connected to voltage sources, and device models need to be defined for the devices in the instance section in the DSPF file. For running the SPGS feature, Spectre is run as in the regular EMIR flow, as shown below.

spectre +aps input.scs +emir=spgs.conf

The SPGS report provides a list of the pin to tap node resistors ordered highest to lowest, as shown below.

It is recommended to run the SPGS feature separately and not together with any other EMIR analysis. SPGS also supports the conversion between pin, tap node, and sub node. The following statements specified in the emir conf file convert the tap node, MPM3@44:s of net I1.vdd to a pin, and the subnode VDD:5 to a tap node.

spgs tap2pin net=[i1.vdd] include=[MPM3@44:s]
spgs sub2tap net=[i1.vdd] include=[VDD:5]

Solid Shape Highlighting

The rail analysis plots that are displayed on the Virtuoso Layout can be viewed as either stick diagrams or solid shape highlights. In the solid shape display, the plots highlight the full shape of the presistors, while in the stick diagram display, the presistors are connected with thin lines over the layout shapes.

The solid shape display is more useful for designers because it allows them to see the shapes that are failing the analysis. There are two flows for solid shape display. You can either specify the DFII layer map file or the Quantus run name for viewing solid shape display for plots. When you specify the Quantus run name, the plots are displayed based on the shape database generated by Quantus.

Quantus Shape Database-Based Flow

To display plots using the shape database generated by Quantus, you must ensure the following:

Support for Specifying Cut-Layers for Metal Layers while Highlighting Solid Shapes

In Voltus-Fi, cut-layers can be specified for metal layers for displaying the EMIR result plots. The cut-layers do not actually chop the shapes on the metal layers in the layout, but when plotting the results, while the shapes on the metal layers are highlighted, those on the specified cut-layers are not highlighted. This helps to view more accurate plots.

An example of a plot is shown below. In this plot, the shapes on metal layer, M1 are highlighted while those on the cut-layer, CM1 are excluded.

To let you specify cut-layers for metal layers, the following SKILL function is provided:

vsaSetLayersToMergeDuringResultsLoading

Use the SKILL function to specify the metal layer and the corresponding cut-layer as a pair. For example,

vsaSetLayersToMergeDuringResultsLoading("M1 CM1A")

where CM1A is the cut-layer for metal layer, M1.

The above SKILL function must be called before loading the results in Voltus-Fi.

Following are the key aspects of this feature:

Display of Finer Color Gradient for Selected Layers in IR and EM Plots

In the DFII layer map flow, for solid shape display of IR/EM violations on the Virtuoso layout, Voltus-Fi-XL locates all the nodes lying on a shape and then colors the shape with the worst violation value among all resistors connected to these nodes.

However, sometimes resistors do not align well with the shapes used to display the violations. This may be because the shapes are large and have multiple nodes and resistors. Voltus-Fi supports a finer display of the color gradient for violations in different segments of such layers. The shape polygons are split into subpolygons and then the subpolygons are colored with the worst violation value for all resistors connected to the nodes in the split shape. This feature is turned on by default for all layers. However, you can select specific layers to view their finer gradient instead of viewing for all layers.

For this, specify the DFII Layermap file and then click the Finer Gradient button provided on the IR or EM tabs of the IR/EM Results form. In the Finer Gradient Layer Selection pop-up, click Deselect All and then select the PGDB layers for which you want to view finer gradient.

Perform this step before loading the IR or EM Results. After loading the results, when you click Show Plot, you can see the finer gradient for the selected layers.

A comparison of finer gradient display versus the original display is shown in below figure.

Specifying Multiple Simulation Result Files for EMIR Analysis

While performing EMIR analysis in Voltus-Fi-XL, multiple bin files can be specified, both in the GUI mode as well as in batch mode. There are two different use models for specifying multiple bin files depending upon whether they are present in the same or different directories.

Specifying Multiple Bin Files in Different Directories

To specify multiple bin files located in different directories, follow these steps:

  1. Open the IR/EM Results form.
  2. Click the + button is provided for the State Directory/Results File field. This button is provided on both the IR and EM tabs of the IR/EM Results form.
  3. The Select MMSIM Results File pop-up window opens. Use this to add multiple bin files for EMIR analysis.

Specifying Multiple Bin Files in the Same Directory

To specify multiple bin files located in the same directory, follow these steps:

  1. Open the IR/EM Results form.
  2. Click the browser button next to the State Directory/Results File field. The Select MMSIM Results File pop-up window opens.
  3. Open the directory containing all the bin files. In the Files of type field, only the bin files will be visible. This is shown below.
  4. Any sub-directories in this directory will also be visible and can be selected.
  5. Select all the bin files that are required and click Open.
In the above flow, the + button located next to the State Directory/Results File field on the IR tab of the IR/EM Results form is not needed for selecting multiple bin files.

Batch Mode Support for Specifying Multiple Bin Files

In batch mode, different options of the vfibatch command are used to specify multiple bin files in different scenarios. The following use models are supported:

Viewing the IR Drop Analysis Results

To plot EMIR results in Voltus-Fi-XL, ensure the following:

Follow these steps to view the IR drop analysis results.

  1. In the Voltus-Fi-XL console, choose IR/EM Analysis – Rail Analysis Results.
    The IR/EM Results form opens.
  2. Click the IR tab to plot the IR drop analysis results.
  3. In the Results group box, specify the State Directory / Results File that stores the results of the simulation. The naming convention of the result file is *.emir#_bin.
  4. Select the + button to specify multiple result files or bin files.
  5. Specify the Shrink factor, if any, by which the xDSPF was shrunk.
  6. Click Customize Display to select the nets for which you want to view the display.
    The Customize Display button is enabled only before the results are loaded. It is disabled once the results are loaded.
  7. Specify either the QRC Run or the DFII Layermap.
    When either of these options is specified, the plots displayed in the layout show solid shape highlighting.
    • If you select QRC Run, specify the path to the QRC Run Directory and the QRC Run Name, respectively.
    • If you select DFII layermap, you can also create a new layer map file or edit an existing file, using the edit button provided next to the field.
  8. For the DFII layer map flow, click Finer Gradient to view the finer gradient for the selected layers.
  9. Click Load Results.
  10. From the Rail Analysis list, select the type of plot you want to view.
  11. Select the nets for which you want to view the IR plots.
  12. Click Select All Nets to select all the nets listed in the table.
  13. Specify IR threshold for viewing IR drop violations above the specified threshold value.
  14. Click Show Plot to view the plot on the Virtuoso layout.
    The IR plot for all power nets appears, as shown below.
    The IR plot for selected nets appears, as shown below.

Related Topics

Displaying and Querying EMIR Results

Voltus-Fi-XL lets you specify the plot display settings for the IR drop and EM plots that are displayed on the Virtuoso layout.

The plot display options include a Min - Max slider that lets you customize the range of violations you want to view. A continuous RGB gradient is used to highlight the worst violation regions in the design. The vast range of color options provided by the RGB gradient makes it easier to view a range of violations in the layout. The available plot display options of the IR/EM Results form are shown in Figure 7-3.

The details of specifying the display options in this form are provided in Specifying the Display Options for IR/EM Plots section.

In addition to specifying settings for plots displayed in the layout, there are options to query the layout for viewing specific violations. The results of the query are highlighted in the EM/IR tab of Annotation Browser.

The following topics are covered in this section:

Viewing EMIR Violations in Annotation Browser

Annotation Browser lets you view and manage violation markers generated for the design. When you click Violation Browser in the IR/EM Results form, Annotation Browser window appears in the upper-right corner of the Virtuoso layout window, and the EM/IR tab opens by default.

The following topics are covered in this section:

The EM/IR tab is used for viewing the violations of IR drop and EM analyses, and it is enabled only when Voltus-Fi-XL is launched. The number of violations displayed in the EM/IR tab is based on the number specified in the Elements count field in the IR/EM Results form.

The check state of a violation marker is saved in the EM/IR tab of Annotation Browser and is reloaded when you start a new Virtuoso session.

Information Displayed in the EM/IR Tab of Annotation Browser

The following information is available in columns in the EM/IR tab of Annotation Browser. The columns that are displayed vary for different analyses types. The complete list of available columns is provided below.

By default, the columns displaying the resistor/node name, layers, and violation values are visible for all types of plots.

The information about columns available for different analyses types for IR plots is provided in the Types of IR Drop Analysis Plots section in this chapter and for EM plots in the Types of EM Analysis Plots section of the “EM Analysis Results” chapter.

You can add or remove columns to customize the information you want to view in Annotation Browser. For this, right-click the column heading, select Columns from the list, and then select the columns you want to view in the tab. This is shown below.

Figure 7-2 Selecting Columns in the EM/IR Tab

Information Displayed in the Description Section of Annotation Browser

Detailed information about the selected node is provided in the Description section of Annotation Browser. For example, for an RJ JMAX analysis type, the following information is provided:

Net = VSS Resistor=ri875 RJ value=3.155 layer=mt1 co-ordinates=(12.017000-23.025000,11.225000-23.020000) resistance=0.247689 length=0.7875um width=0.24um needed Width=0.757201um

For an IR drop analysis type, the following information is provided:

Node=459 VSS#453 IR value=0.00495278 co-ordinates=(58.334999 27.959999) layer=mt1 Net=VSS Time=7.64774e-08

You can view the units for corresponding values in the description section.

The entries in Annotation Browser honor the user-specified plot display settings in the display options specified in the IR/EM Results form. Therefore, the results of the query comply with the user-specified plot settings.

For more information about how to use Annotation Browser and manage the different views, see the “Layout XL Assistants” chapter in Virtuoso Layout Suite XL User Guide.

Querying EMIR Results

The following layout query features are supported in Voltus-Fi-XL.

Specifying the Display Options for IR/EM Plots

After you load the IR drop or the EM analysis results on the IR and EM tabs of the IR/EM Results form, select the nets for which you want to view the plots, and click Show Plot. The IR/EM Results form expands to provide options for customizing the plot display in the layout.

Use the scroll bar provided at the bottom of the form to view the display options. Click the arrow provided on the top-left corner of the form to hide or unhide the Display form. This is shown in Figure 7-3.

The following topics are covered in this section:

Selecting Layers for Viewing Violations

The following options are provided in the Layers group box of the Display form for selecting layers:

Customizing the Range for Viewing Violations

The following options are provided in the Display form for customizing the range for viewing violations.

Customizing the Display Options for Plots

The following options are used to customize the plot displays:

Viewing and Managing Violations in the layout

The following options are provided in the Action group box of the Display form for viewing and managing violations on the Virtuoso layout:

Viewing Worst Violations

Click Zoom Select Max Violation to zoom into and highlight the maximum violation in the selected area in the layout. For this, first click Zoom Select Max Violation, and then select an area in the layout to locate and zoom into the maximum violation in that area. Annotation Browser opens and the node or presistor with the worst violation in the selected area is highlighted in the browser.

In addition, the maximum violation in the selected area is marked on the ruler in the IR/EM Results form with a red arrow. This is shown in the image below.

Figure 7-9 Zooming into the Maximum Violation in the Selected Area

Viewing all Violations in Selected Area

Click Get Value on Layout to retrieve the values of violations in the selected area from the layout view. For this, first click Get Value on Layout and then select an area in the layout. The violations in the selected area are marked on the ruler with red arrows and are highlighted in Annotation Browser. If there are multiple violations in the selected area, all violations will be marked in Annotation Browser. This is shown in the image below.

Figure 7-10 Retrieving Violation Values from the Layout

Querying Specific Points and Areas in the layout for Resistor Information

Select Query to display the resistor information for a point or points within a specified area in the layout. For this, first select Query and then use the left mouse button to click any point or to select an area in the layout.

The Layer Selection for Query form opens. In this form, select the layers for which you want to perform the query and click OK. By default, all layers that are selected in the Layers group box of the Display form are selected in this form. This form is shown below.

Figure 7-11 Layer Selection for Query Form

The above form opens when multiple layers are selected in the Layers group box or the layer selection window.

The result of the query or the resistor information for the selected point or for points in the selected area is displayed in the Query Box.

You can add or remove columns to customize the information you want to view in the Query Box. To do this:

To rearrange the columns:

To save the configuration:

Different information is displayed in the query box depending upon whether the query is for IR drop, EM analysis, SHE analysis, or RMS hot-spot waiving analysis. This is covered in the following sections:

Query Box Information for IR Drop Analysis

The following information is reported in the Query Box columns for IR drop analysis query:

  1. name: The name of the resistor for which information is being queried
  2. layer: The name of the layer on which the resistor is located
  3. netName: The net name of the resistor
  4. node1: The name of the first node of the resistor
  5. node2: The name of the second node of the resistor
  6. IRmaxNode1(mA): The maximum IR drop on node 1 in milliampere
  7. IRmaxNode2(mA): The maximum IR drop on node 2 in milliampere
  8. IRavgNode1(mA): The average IR drop on node 1 in milliampere
  9. IRavgNode2(mA): The average IR drop on node 2 in milliampere
  10. Ipeak(A): The peak current of the resistor in ampere
  11. Iavg(A): The average current of the resistor in ampere
  12. Irms(A): The RMS current of the resistor in ampere
  13. layerType: The layer type, metal or via
  14. x(um): The x-coordinate of the resistor in micrometer
  15. y(um): The y-coordinate of the resistor in micrometer
  16. Reff: The effective resistance value of the resistor. The effective resistance values are displayed only when effective resistance plot type is selected. For other IR drop analysis plots, NA is displayed in the query box column.
  17. Number of Shapes: The number of shapes in power net layout

A part of a sample query box for querying a selected area for IR drop analysis is shown below.

Figure 7-13 Displaying IR Drop Analysis Query Results for a Selected Area in the Query Box

Query Box Information for EM Analysis

The following information is reported in the Query Box columns for EM analysis query:

  1. name: The name of the resistor for which information is being queried.
  2. layer: The name of the layer on which the resistor is located.
  3. netName: The net name of the resistor.
  4. node1: The name of the first node of the resistor.
  5. node2: The name of the second node of the resistor.
  6. type: The layer type, metal or via.
  7. current_direction: The current direction of the resistor.
  8. Iavg_rule: The EM rule used for average analysis.
  9. Ipeak_rule: The EM rule used for max/peak analysis.
  10. Irms_rule: The EM rule used for RMS analysis.
  11. Iacpeak_rule: The EM rule used for AC peak analysis.
  12. x(um): The x-coordinate of the resistor in micrometer.
  13. y(um): The y-coordinate of the resistor in micrometer.
  14. w(um): The width of the resistor in micrometer.
  15. l(um): The path length in micrometer.
  16. Ipeak(A): The peak current of the resistor in ampere.
  17. Iavg(A): The average current of the resistor in ampere.
  18. Irms(A): The RMS current of the resistor in ampere.
  19. Iavg_max(A): The maximum average Current Density in ampere.
  20. Ipeak_max(A): The maximum peak Current Density in ampere.
  21. Irms_max(A): The maximum rms Current Density in ampere.
  22. acpeak_max(A): The maximum AC peak Current Density in ampere.
  23. delta_T(C): The rise in temperature of the resistor caused due to Joule heating in degree Celsius.
  24. Td(us): The total on-time period in microsecond.
  25. r: The duty ratio.
  26. a(um^2): The area of the via in micrometer square. In case of metal layer, the value will be "-".
  27. N: The number of vias in the via array. In case of metal layer, the value will be "-".

A part of a sample query box for querying a selected area for EM analysis is shown below.

All columns in the EM analysis query are not visible in the query box when it opens. Use the scroll bar to see more information in the query box.

Figure 7-14 Displaying EM Analysis Query Results for a Selected Area in the Query Box

Query Box Information for SHE Analysis

The following information is reported in the Query Box columns for SHE analysis query in addition to that displayed for EM analysis:

  1. feolT(C): The self-heating coupling temperature in degree Celsius.
  2. beolT(C): The temperature in degree Celsius caused by Joule heating and self-heating coupling.
  3. Iavg_sh(A): The average current of the resistor in ampere while performing SHE analysis.
  4. Iavg_sh_max(A): The maximum average Current Density in ampere while performing SHE analysis.

Query Box Information for RMS EM Hot Spot Waiving Analysis

The columns below are displayed when the RMS EM hot spot waiving analysis is enabled, which is a limited-access feature:

The RMS EM hot spot waiving analysis, is a limited-access feature. To use this feature, contact your Cadence representative and explain your usage requirements.
  1. rms_%fail: The pass or fail percentage for RMS EM analysis
  2. avg_%fail: The pass or fail percentage for average EM analysis
  3. rms_minW(um): The minimum width in micrometer required for the metal layer resistors to pass the RMS EM violation
  4. rmsT(C): The temperature of the resistor in degree Celsius caused by its own Joule heating
  5. jouleHeatT(C): The temperature of the resistor in degree Celsius caused by its own Joule heating and that of neighboring resistors
  6. Tmetal(C): The effective temperature of the resistor in degree Celsius, which also includes the temperature caused by Joule heating.
  7. PG_wire: Indicates whether or not supply net exists in the allowed range of the resistor
  8. rms_waived: Indicates whether or not RMS violation is waived
The Query Box displays results for the first thousand entries at one time. If your query results in more than 1000 entries, the following pop-up box is displayed:

When the Query check box is selected, the left mouse button is used to click a point or select an area in the layout. At this time, you cannot perform any other operation with the left mouse button. To use this button for any other layout operation, deselect the Query option.

Highlighting Query Results in the layout

For the query results listed in the Query Box window, you can highlight the resistor in the layout. You can select multiple rows to highlight multiple resistors at the same time.

In the figure below, you can see the two resistors selected in the query box are highlighted in the layout in white. This is shown using a red text box for better visibility.

Figure 7-15 Highlighting Query Results in the layout

Saving the IR Drop Analysis Result Plots and Reports

The following options are provided for saving the plots and reports of IR drop analysis results:

Comparing Reports

The Display form provides an option to compare reports for different analysis types that are generated in the GUI and batch mode. For this, click Compare Report in the Display form.

Figure 7-17 Comparing Reports

The pop-up window, Compare Reports, opens. In this window, you can perform the following tasks:

Types of IR Drop Analysis Plots

All rail analysis plots are available in the list in the Rail Analysis field in the IR/EM Results form.

Following types of IR drop analysis results plots are available:

IR, IRAVG – IR Drop Plots

Analyzes and reports voltage drop. The IR drop plot is displayed on the Virtuoso layout. The IR drop data is saved inside the state directory or the simulation result file of the net. The worst case voltage drop can be displayed using the Violation Browser check box. The segments of the design with high IR drop can then be debugged.

There are two types of IR plots available in the list – IR - IR Drop and IRAVG - IR Avg Drop. The IR Drop plot displays the peak voltage drop while the IRAVG plot displays the average voltage drop.

If in the emir.conf file in the bin directory, the report_voltage variable is set to true, the IR plots will display absolute voltage values instead of the IR drop values.

Information Displayed in Annotation Browser for IR Drop Analysis

The EM/IR tab of Annotation Browser displays the following columns for this analysis type:

The IR plot is shown in the Displaying and Querying EMIR Results section.

RC, RCAVG, and RCRMS – Resistor Current Plots

Analyze and report resistor currents. After observing IR drop plots, the next step is to understand how the current flows in the design to create the generated IR drop plot. It is important to examine resistor currents (RC) plots because they exhibit behaviors that are not obvious from examining only IR drop plots. The RC plots show current-flow trends that you either might not have expected or current from several power pins reconverging in the middle of the chip to create high currents in some wires.

There are three types of RC plots available in the list – RC - Resistor Current, RCAVG - Average Resistor Current, and RCRMS - RMS Resistor Current.

The RC - Resistor Current plot is available for all analysis types for both IR drop and EM analysis results (both for the qrcTechFile and emDataFile flow).
The RCAVG and RCRMS plots are available for all analysis types for viewing the IR drop results but only available in the qrcTechFile flow and the EM Only ICT File flow for viewing the EM analysis results. These plots are not available in the emDataFile flow.

Information Displayed in Annotation Browser for RC Plot Types

The EM/IR tab of Annotation Browser displays the following columns for RC - Peak, RCAVG, and RCRMS plot types:

The plots shown below display peak and average resistor currents. The violation range is customized by using the Min Max sliders in the IR/EM Results form.

Figure 7-19 RC – Peak Resistor Current Plot

Figure 7-20 Average Resistor Current Plot

IV – Transistor Voltage Plot

Analyzes and reports the voltage drop at device nodes, also known as tap nodes.

Information Displayed in Annotation Browser for Transistor Voltage Plot Type

The EM/IR tab of Annotation Browser displays the following columns for transistor voltage plot type:

This plot is shown below.

Figure 7-21 Transistor Voltage Plot

TC, TCAVG, TCRMS – Tap Current Plots

Analyze and report tap currents. These plots show the current distribution inside the transistor. The power-grid library generation program characterizes the distribution of the current inside the transistor and replaces the devices connected to the power grid with current taps (sink). The relative distribution of the current inside the transistor power-grid view library is based on the device width and length.

If an accurate power-grid view is used for the memories during rail analysis, the tap current plots clearly highlight the low current distribution in the transistor region and high power distribution in the sense amplifier and the decoder circuit of the memory.

There are three types of TC plots available in the list – TC - Peak Tap Current, TCAVG - Average Tap Current, and TCRMS - RMS Tap Current.

Spectre simulation should be run with the report_tapi=on option specified in the EMIR configuration file to output the rms, avg, and max tap currents in the .emir#_bin simulation result file.
The TC - Peak Tap Current plot is available for all analysis types for both IR drop and EM analysis results.
The TCAVG and TCRMS plots are available for all analysis types for viewing the IR drop results but only available in the qrcTechFile flow and the EM Only ICT File flow for viewing the EM analysis results. These plots are not available in the emDataFile flow.

Information Displayed in Annotation Browser for Tap Current Plot Types

The EM/IR tab of Annotation Browser displays the following columns for TC - Peak, TCAVG, and TCRMS plot types:

For details about the information displayed in the columns of Annotation Browser, see Information Displayed in the EM/IR Tab of Annotation Browser.

The plot shown below displays peak tap currents. The violation range is customized by using the Min Max sliders in the IR/EM Results form.This plot is shown below.

Figure 7-22 Peak Tap Current Plot for All Power Nets – Displaying Total Violation Range

POWER – Resistor Power Plots

Analyze and report resistor power, which is the value of current through a resistor multiplied by the voltage across the resistor.

Information Displayed in Annotation Browser for Resistor Power Plot Types

The EM/IR tab of Annotation Browser displays the following columns for Resistor Power plot types:

For details about the information displayed in the columns of Annotation Browser, see Information Displayed in the EM/IR Tab of Annotation Browser.

The plot shown below displays resistor power plot for the top ten violations.

Figure 7-23 Resistor Power Plot – Displaying Top Ten Violations

Click Save Report in the Display form to save the report for this plot. You can open the report for viewing. A sample report is shown below. The reporting for this plot is only supported in the GUI mode.

Figure 7-24 Sample Report for Power - Resistor Power Plot

PI – Powergate Current Plot

This plot is applicable only to power-gated design and analysis.

This plot displays the currents across resistors when power gates are connected.This plot is used to analyze whether the current through power gates exceeds the saturation current or not, and if it does, to debug such instances in the design. The saturation current and the on-resistance of the power switches are characterized and stored inside the power-grid library of the power-gate transistor.

Information Displayed in Annotation Browser for Powergate Plot Types

The EM/IR tab of Annotation Browser displays the following columns for both, powergate current and powergate voltage plot types:

This PI plot is shown below. In this plot, the resistor with the maximum current violation is zoomed into using the Zoom Select Max Violation option in the IR/EM Results form.

Figure 7-25 Powergate Current Plot

A sample PI report is shown below:

PV – Powergate Voltage Plot

This plot displays the IR drop across power-switch instances. This plot can be used to analyze and debug the regions of IR drop inside the power-gated block. For example, if the IR drop, across power gate is already high, the IR drop inside the power-gated block will be much higher. In this case, the power-gate placement will have to be refined or more power gates will have to be added to resolve the IR drop problem.

This plot is shown below.

Figure 7-26 Powergate Voltage Plot

A sample PV report is shown below:

REffective – Effective Resistance Plot

Uses the data generated by the static power grid solver (SPGS) to display the pin-to-node resistances on the Virtuoso layout. For more information about how resistances are calculated and reported by the SPGS, see the Static Power Grid Solver section.

In this plot type, you can also plot the least-resistive path for a net. For details, see Plotting the Least-Resistive Path.

The effective resistance plot for all nets is shown below.

Figure 7-27 REffective Plot for All Nets

Plotting the Least-Resistive Path

The least-resistive path (LRP) plot lets you identify weakly connected instances in the design during early stages of power planning. The resistance for an instance pin is calculated as the total resistance along the least resistance path. If an instance has multiple power pins connected to the power grid, the LRP plot uses the pin with the worst (highest) resistance value to plot the instance-based data. This plot highlights the current path for the selected instance to the voltage source. A long LRP usually results in high resistance and potentially high voltage drop.

In addition to identifying and displaying the worst IR drop violations, the LRP feature in Voltus-Fi-XL lets you plot LRP on demand for any node. You can view the LRP for any high IR drop node by selecting it in the layout. There are two options provided in the GUI, Get Layout Node and Get Marker Node, to let you select a node on the GUI and view its LRP and to select an object in Annotation Browser and view the LRP for the node on the selected marker. For details, see The LRP Browser and Displaying LRP for the Node on the Selected Marker, respectively.

Batch Mode Support for LRP Analysis

The following batch commands is used for loading and printing RLRP analysis reports in Voltus-Fi-XL:

Batch Mode Support for LRP Analysis

The following batch commands is used for loading and printing RLRP analysis reports in Voltus-Fi-XL:

Tcl Commands:

An example of the set of Tcl commands for loading and printing the LRP analysis reports is as follows:

load_ir_results\
./abc/raw.out/xps.emirtap.emir0_bin\
print_rlrp_report \
-net TVDD \
-filename RLRP.rpt \
-tap MavD7_1_unmatched#d \

The detailed description, syntax and examples of how to use these commands are provided in the load_ir_results section of the “Batch Mode Execution” chapter.

GUI Support for LRP Analysis

The use model for LRP analysis is detailed below. To view the LRP plot for a net, perform the following steps after loading the IR drop analysis results:

The LRP Browser

The LRP Browser tab lets you specify nets, layers, and nodes for which you want to view the LRP plots. The various options provided for this are detailed below.

Voltus-Fi-XL provides support in the form of tips about the information to be filled out in the various fields in the LRP Browser form. This tooltip appears when you hover over a field in the form. This is shown below.

Figure 7-29 Tooltips for LRP Browser Tab

To start, click the LRP Browser tab of the IR/EM Results form. The form shown below opens.

Figure 7-30 LRP Browser Tab of the IR/EM Results Form

There are two group boxes in this tab, the LRP Paths and Resistance Path.

If the tables in the LRP browser tab do not show any entries, ensure the following:

Resistance Path Group Box Table Information

The Resistance Path table lists all resistors in the LRP path for the node selected in the Node ID - Node Name table. You can click any row to highlight the resistor in the layout window.

A part of the Resistance Path table is shown in the image below. The details of the column information is provided subsequently.

Figure 7-34 Information in the Resistance Path Table

It provides the following information:

Shorting Layers for LRP Analysis

While computing LRP for a node or instance, you can short specific layers. When you do this, all resistance on the specified layer is shorted, that means, the LRP display shows a value of 0 for all resistors on the shorted layer. This is shown in below images.

When you click Shorted layers, the Filters pop-up window opens. In this window, select the layer you want to short. You can short multiple layers.

For example, in the image below, layer Metal2 is shorted.

Figure 7-35 Specifying the layers to be shorted for the LRP Analysis

When a layer is shorted, the Layer information in the Resistance Path group box shows a value of 0 in the R val (Ohm) column for all resistors on that layer. For example, in the image below, the LRP value for resistor, rh740 on layer, m2 is 0.

Figure 7-36 LRP Value for Resistors on the Shorted Layer

Displaying LRP for the Node on the Selected Marker

You can display the LRP for a node on the selected marker in Annotation Browser. When you select a violation marker in the Browser, it is highlighted in the layout. If the marker is associated with a node name, you can view the LRP for the node. This is particularly useful when either REffective or the transistor voltage plot is being shown and you want to see the LRP for the selected marker node.

The steps are detailed below.

Supporting LRP Analysis in Power-Gated Designs

In Voltus-Fi-XL, you can view the LRP plot for power-gated designs. An always-ON net LRP plot shows LRP path for all nodes in the always-ON net as well as for all nodes connected to the switched net.

The steps performed to select the LRP analysis type in the IR/EM Results form are the same as those described in the previous section. In addition, select the always-ON net. For example, the net TVDD, shown below is an always-ON net.

The net, VDD!, shown in below image, is a switched net.

Figure 7-38 Selecting the Always-On Net for Viewing the LRP

Select the LRP Browser Tab. This is shown below.

Figure 7-39 LRP Browser Tab for Power-Gated Designs

In the above form, the LRP Paths group box displays the LRP values for the nodes connected to the always-ON net. It also shows the LRP values for the nodes connected to the switched net.

The table in the Resistance Path group box shows the resistance for the node selected in the LRP Paths table above.

The resistance value of the resistor, "rON", is assumed to be zero ohms.
To view the demonstration on performing the LRP analysis in Voltus-Fi, see Plotting the Least Resistive Path (LRP) video.
Access to this video will depend on the availability of a web browser and a Cadence Online Support account.

LRP Reports

You can create RLRP reports in batch mode by using the print_rlrp_report. You can also generate and view the report by using the print report option in the LRP Browser tab in the GUI. You can specify the name of the report file and click Save. The report opens in the console. A sample report is shown in Default Reports Generated for EMIR Analysis.

Calculating Effective Resistance between any Two Nodes on a Net

In Voltus-Fi-XL, you can calculate the effective resistance between any two nodes (pins, tap nodes, or subnodes), either on the same net or on different layers of the same net. This feature is supported both in the GUI and in batch mode.

This feature uses the DSPF file, used for Spectre simulation, and the SPGS feature of Spectre. It works only for IR drop analysis. For more information about the SPGS flow, see Static Power Grid Solver.

To run this feature, it is recommended that you use MMSIM/Spectre 15.1.0 ISRx and later versions.

Batch Mode Support for Calculating Effective Resistance

The following batch commands are used for calculating the effective resistance between nodes in Voltus-Fi-XL:

Tcl Commands:

An example of the set of Tcl commands for reporting the effective resistance between two nodes is as follows:

load_ir_results \
./abc/raw.out/xps.emirtap.emir0_bin
pin_2_pin_res \
-xdspf abc/raw.out/abc_sample.dspf \
-x1 83.40 \
-y1 34.205 \
-x2 83.40 \
-y2 35.205 
-layer1 mt1 \
-layer2 mt2 \

-net VDD

For details, see the load_ir_results in the “Batch Mode Execution” chapter.

GUI Support for Calculating Effective Resistance

In the GUI mode, this feature is enabled through the Pin2PinR tab provided in the IR/EM Results form. By default, this tab is disabled. To enable this tab, perform the following steps:

The Pin2PinR tab is enabled. This is shown below.

Figure 7-40 IR/EM Results form – Pin2PinR Tab

To calculate effective resistance between two nodes on a net, provide the following information on this tab:

To view the demonstration performing pin-to-pin resistance check in Voltus-Fi, see Calculating Effective Resistance between any Two Nodes on a Net video.
Access to this video will depend on the availability of a web browser and a Cadence Online Support account.

Generating EMIR Analysis Reports in Voltus-Fi-XL

The following topics are covered in this section:

Reports Generated Using the EMIR Control File

You can generate EMIR reports in text, HTML, or CSV format by specifying the EMIR control file (emir.conf), the EMIR database file, and the output directory. In the EMIR control file, the report option of the emirutil command is set to text, html, or csv depending upon the required output.

For example, emirutil report=text generates a text report. Similarly, emirutil report=csv generates a report in a compressed tar file. A CSV report is available on unzipping or untarring this file.

The syntax of the command to generate EMIR reports in text, HTML, or CSV format is as follows:

vfibatch -control <confFileName> -db <binFileName> -outdir <outDirName>

For example,

vfibatch -control emir.conf -db xps.emir0_bin -outdir out1

or,

emirreport -control emir.conf -db xps.emir0_bin
Specifying the output directory is optional.

The syntax of the command to generate EMIR reports using multiple bin files is as follows:

vfibatch -control emir.conf.report -db "binFileName1 binFileName2"
For details of the supported EMIR control file options that can be specified, see EMIR Control File Options Supported in Voltus-Fi-XL.

Format of IR Reports

An IR report is generated in the following default format depending on which command is run:

However, you can change the format of the report as follows:

Default Reports Generated for EMIR Analysis

By default, Voltus-Fi-XL generates the following reports for EMIR analysis:

All default reports print the software version number in the header. You can view this in the sample reports shown in the subsequent sections.

The following reports are detailed:

IR Report Format

In the IR drop analysis report file, information is provided in the following format for each net. The type of analysis is mentioned for each net.

----------------------- "VDD" NET: Vref = 2.500000V -------------------------------
max
Resistor   ir value   Layer   X1   Y1   X2   Y2   Res   Length   Width   Ipeak  

Sample IR Drop Analysis Report

A part of the sample IR drop analysis report is shown below.

_______________________________________________________________________

VOLTAGE DROP RESULTS
VERSION = v06.17-e021_1
BINARY FILE          = /home/anuk/MMSIM_EMIR_WORKSHOP/emir_simulation/aps.direct.raw/input.emir0_bin
RESULTS FILE CREATED = 2015-Dec-16 23:15:18 (2015-Dec-17 07:15:18 GMT)
USER SUPPLIED VALUES:
   RESULTS TYPE      = TRANSIENT
   TRANSIENT START   = 0
   TRANSIENT STOP    = 1.2e-07
   SIM TEMPERATURE   = 27 C
   AVERAGE           = nil
   PEAK              = t
   SIGVMAX           = t
   SIGVAVG           = nil
-------------------- "VDD" NET: Vref = 2.500000V -------------------------------
max
Resistor     ir value        Layer      X1       Y1       X2       Y2 
                                                                                     
ri293        0.00713207      mt1        37.56    45.32    37.56    47.92
ri292        0.00713193      mt1        37.56    40.38    37.56    45.32
ri291        0.00712603      mt1        37.56    38.04    37.56    40.38
ri290        0.0071256       mt1        37.56    35.44    37.56    38.04
ri289        0.00712512      mt1        37.56    30.5     37.56    35.44

EM Report Format

In the EM analysis report file, information is provided in the following format for each net. The type of analysis is mentioned for each net.

----------------------- NET "VDD" -------------------------------
avg
Pass/Fail %   Resistor   layer   Current   Width   PathLength I_limit X1   Y1   X2   Y2   J/JMAX   Res   ViaArea   No of needed width/#via   J_limit

Sample EM Analysis Report

The image below shows a part of the EM analysis report.

The table below lists the analysis type and the corresponding section heading in the EM report file.

EM analysis type Section heading in the EM Report File

Average

avg

Peak

max

RMS

rms

Absolute Average

Absavg

Generating a Report for All Resistors

You can generate a report to view the resistor information for all resistors in the design. To generate this report, use the emirutil command to set reportAllResistor to true in the EMIR configuration file.

emirutil reportAllResistor=true

For more information, see EMIR Control File Options Supported in Voltus-Fi-XL in the “Data Preparation” chapter.

A report, with the suffix, “#.rpt_all” is generated. The format of the report is the same as that of the “.#rpt_em” report.

Pin Current Report Format

In the pin current report file, the Imax, Iavg and Irms currents for pins for each net are reported.

-----------------------NET "VDD"------------------------------
Name         Imax         Iavg         Irms

Sample Pin Current Report

A part of a sample pin current report is shown below.

Summary Report Format

In the summary report, there are two tables of information for each net.

The first table provides, in its header, the name of the net, the simulation temperature, and the measurement window or the start and stop time for the analyses. For each net, the table lists the layer name and the corresponding maximum value of each analysis type for that layer. Information for different types of analyses is displayed in different columns.

The format of the first table is as follows:

_______________________________________________________________________
Net name           GND            
Sim temperature    125            
Measurement window   0 - 5.9e-08 
_______________________________________________________________________
Layer            iavg
_______________________________________________________________________

The second table lists the layer names. For each layer and analysis type, there are two columns of information. The first column lists the number of resistors on which the analysis was run (analysistype_run_on) and the second column lists the number of resistors that were ignored in the analysis (analysistype_num_skip). The two columns are repeated for different types of analyses.

The format of the second table is as follows:

_______________________________________________________________________________
Layer    analysistype1_run_on   analysistype1_num_skip   analysistype2_run_on   analysistype2_num_skip   
_______________________________________________________________________________

Sample Summary Report

The image below shows a part of the summary report:

___________________________________________________________________
Net name           GND            
Sim temperature    125            
Measurement window   0 - 5.9e-08    
___________________________________________________________________________
Layer              vmax               irms               iavg               imax               
___________________________________________________________________________
metal1             0.0137511          0.0541541          1.92388            0.339854           
metal2             0.0098085          0.541685           11.6608            0.478398           
metal3             0.00587761         0.227175           1.9191             0.445334           
metal4             0.00451982         0.109318           0.778421           0.11097            
n_odcont           0.022525           0                  0.425099           0                  
n_poly             0.00261004         0                  0                  0                  
n_polycont         0.00261902         0                  2.87543e-08        0                  
p_odcont           0.00614363         0                  0.146129           0                  
p_poly             0.00261004         0                  0                  0                  
_______________________________________________________________________
Layer              vmax_run_on vmax_num_skip irms_run_on irms_num_skip   
_______________________________________________________________________
metal1             15537       0             15537       0             
metal2             7253        0             7253        0             
metal3             2253        0             2253        0             
metal4             616         0             616         0             
n_odcont           6526        0             0           6526          
n_poly             222         0             0           222           
n_polycont         80          0             0           80            
p_odcont           3291        0             0           3291          
p_poly             34          0             0           34            
__________________________________________________________________________
Net name           VDD            
Sim temperature    125            
Measurement window 0 - 5.9e-08
__________________________________________________________________________
Layer              vmax               irms               iavg               imax               
__________________________________________________________________________
metal1             0.0288203          0.0742177          1.0235             0.621502           
metal2             0.0141003          0.46877            10.0913            1.45709            
metal3             0.00556588         0.191977           1.40789            0.184331           
metal4             0.00391154         0.113201           0.562096           0.106243           
n_odcont        0.00902663       0               0.0742855       0                  
n_poly          0.00260217       0                  0                  0

RLRP Report

RLRP analysis report (RLRP.rpt) includes the LRP values of the instances or tap-nodes of the specified net. In the RLRP analysis report file, information is provided in the following format for each net. 

Shortest path for net <net name> to tap <tap name> : total resistance : <resistance value>
res-name   coordinates   res   layer   length   width   volt   acc-lrp   
acc-volt   node1   node2

Sample RLRP Report

Reports Generated for Multiple Bin Files for Different Nets from the Same Testbench

This section describes the use model for analyzing IR/EM results when multiple emir bin files are available for different nets of the same testbench. This is useful in large designs, where simulation is run separately for different nets to improve the runtime.

In batch mode, the following command is used to generate separate IR/EM reports for multiple bin files:

vfibatch -control emir.conf.report -db "xps.vdd/xps.raw/xps.emirtap.emir0_bin xps.vss/xps.raw/xps.emirtap.emir0_bin" -text abc
The bin filenames are separated by a space as shown above. The -text option is used to specify the name of the result file that will include the results for both nets. In the above example, the following report files will be generated for IR and EM analysis, respectively:
abc.rpt_ir 
abc.rpt_em

Reports Generated for Multiple Bin Files from Different Testbenches in a Design

This section describes the use model for analyzing IR/EM results when multiple emir bin files are available for the same design, but different testbenches. The following reports can be generated for such designs in Voltus-Fi-XL.

Creating the Simulation Deck-Based Reports

This use model requires that the multiple #.emir_bin files should be available in the same directory. For example, test.emir0_bin, test.emir1_bin, test.emir2_bin, and so on.

In batch mode, the following command is used to generate separate IR/EM reports for multiple bin files:

vfibatch -control conf filename -db_path path_of_directory_containing_emir_bin_files -outdir outDirName

For example,

vfibatch -control emir.conf -db_path test/test.raw -outdir out

This command will generate separate IR/EM reports for each emir bin file.

For example, if there are two bin files, test.emir0_bin and test.emir1_bin, then the following reports will be generated:

The format of these reports is the same as that of the default IR/EM reports generated in case of a single emir_bin file run.

Consolidated Reports for All Simulation Decks

A single consolidated EM report and IR report will be generated comprising results from all simulation decks (#.emir_bin files). To enable the generation of consolidated reports, set the following:

The vfibatch command having the option, "-db_path/-db_multi_path" with emir variable "consolidatedReport" set to "true" in the emir configuration file will generate the consolidated reports for both, EM and IR analyses.

By default, when the consolidatedReport option is set to true, the worstResult option is also set to true, which means only the worst violation will be reported. 

emirutil consolidatedReport=true
emirutil worstResult=true

To view all the results in the consolidated report, set the worstResult option to false.

For details of the above options, see EMIR Control File Options Supported in Voltus-Fi-XL in the “Data Preparation” chapter.

There are two possible scenarios in the creation of consolidated reports:

These scenarios are detailed below.

Scenario 1: The emir bin Files are in the Same Directory

In this scenario, there are multiple emir bin files in the same directory. For example, test.emir0_bin, test.emir1_bin, test.emir2_bin, and so on.

To generate a consolidated report in this scenario, use the following command in batch mode:

vfibatch -control conf_file_name -db_path path_of_directory_containing_emir_bin_files -outdir outDirName

The above command uses the -db_path option to specify the path of the directory containing all the bin files.

For example,

vfibatch -control emir.conf -db_path test/test.raw -outdir out

Scenario 2: The emir bin Files are in Different Directories

To generate a consolidated report in this scenario, use the following command in batch mode:

vfibatch -control conf filename -db_multi_path name_of_file_containing_paths_to_emir_bin_files -outdir outDirName

The above command uses the -db_multi_path option to specify the name of the file that contains the paths to the emir bin files containing the simulation results of different testbenches of the same design but in different directories.

For example,

vfibatch -control emir.conf -db_multi_path emir_bin_files -outdir out

Where, the file, “emir_bin_files” contains the following information:

test/test.raw/test.emir0_bin
test1/test1.raw/test1.emir0_bin
test2/test2/raw/test2/emir0_bin

A part of a sample consolidated report is shown below.

Figure 7-43 Sample Consolidated EM Report

Figure 7-44 Sample Consolidated IR Report

In the above report, the IR results for the resistors "ra3" and “ra2” for net VG, and resistor, “rx13” for net, VDD from all emir_bin files are reported. By default, for consolidated reports, the emirutil variable, worstResult is set to true. Therefore, the report only includes the worst result for each resistor, which is the first row of information for each resistor shown in the above report.

However, for the above report, to view all results, the worstResult variable is set to false. In this case, the IR results for the resistors are sorted so that the worst case is reported first and best case is reported last.

Reporting a List of Devices from a Subnode

Voltus-Fi-XL supports tracing of all devices or tap points starting from a metal subnode. This feature lets you list the device tap nodes that are nearest to a given subnode on a metal layer. For this, specify the name of the subnode present on any metal layer and the software will list the tap nodes that are nearest to that subnode. The term “nearest” used here refers to the shortest distance of tap nodes from the subnode in terms of the number of resistors.

To use this feature, the names of the subnodes for which you want to trace the tap nodes must be provided.

The output is a report file containing the tap name of each subnode that is specified in the input.

Use Model

This feature is only supported in batch mode. To use this feature, the following commands and variables are used.

For details of the command parameters, see load_ir_results in the “Batch Mode Execution” chapter.

Sample Command File and Results File

A sample command file and a report file generated from this command file are shown below.

Sample command file

load_ir_results emir0_bin.gz
set_variable subnode_to_tap_path_trace_discard_pattern "MPC"
set_variable subnode_to_tap_path_trace_number_of_taps_to_report 6
print_subnode_to_tap_path_report -net VDD -subnode VDD:36919 -filename subnode_tap_path.rpt

Sample results file

SUBNODE TO NEAREST TAP PATH RESULTS 
BINARY FILE         = emir0_bin.gz
REPORT FILE CREATED = 2016-Sep-24 04:08:45 (2016-Sep-24 11:08:45 GMT)
VDD:36919          23.556  0.68
                   X18_unmatched:s 23.574  0.525
                   XI13/MP1:s  24.03  0.915
                   XI27/MP1:s  24.078  0.915
                   MN6:d  23.622  0.525
                   MP0:s  23.793  0.945
                   MP8:s  23.745  0.945

Reporting On-Resistance (RON) Values

Overview

Voltus-Fi-XL reports the RON values for all layers between specified pairs of pins in a design. The software reports the combined resistance contribution of both pins in the pair and the contribution from each pin. The resistance values are reported in ohms.

For this feature, report_vfi_XL_ron command has been provided. For details, see report_vfi_XL_ron in the “Batch Mode Execution” chapter.

Generating the RON Report

This flow is supported only in the batch mode. To enable this flow, perform the following steps:

Example:

Use the following commands to report RON for IR drop analysis using the pin-pair file, pin_pair.txt in the output file, output.rpt:

load_ir_results …input.raw/input.emir0_bin
report_vfi_XL_ron -pin_pair_file pin_pair.txt -output_file output.rpt

Output

The RON report includes the following information:

Sample Pin-Pair File

VN1 VN2

Sample RON Report

A sample RON report is shown below.

Figure 7-45 Sample RON Report


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