Execution of the HITAS results in the generation of a flat or hierarchical timing database (UTD) describing, in a compressed form, all the timing paths, cone details and interconnect details in the design under analysis. Xtas should be used in order to visualize the information in this timing database. It provides a fast, interactive and user friendly environment in which to perform timing requests. It also provides the means of performing the full static timing analysis and the visualization of accurate timing diagrams for any signals which do not satisfy the constraints.
The XTas tool is used after generation of the UTD. It is used in order to interpret the information in the DTX file. The timing database must first be loaded into XTas. The DTX file contains gate details. In the case of a hierarchical database, it is the top-level DTX file which should be specified.
After loading the database, reference points (connectors, latches, commands, and precharges) can easily be visualized. You can then ask XTas to display critical and near-critical paths based on constraints such as, for example, the display of the ten longest paths ending on a particular point. For any given critical path, it is possible to display instantaneously paths with the same reference points but not the most critical; these are the so-called parallel or near critical paths. Optimization of a critical path is often useless if parallel paths are not similarly optimized.
For any critical or near-critical path, XTas can also instantaneously display the full gate and interconnection details of the path. Unlike most timing analyzers, this is possible even if the path traverses several levels of the hierarchy.
Finally, it is also possible to launch the static timing analysis engine from within XTas. In order to perform this analysis, it is first necessary to create a constraints file (see chapter "Static Timing Analisys" of this Guide). If this file exists alongside the timing database, then a single button launches the analysis after specifying a few options. Any violations are displayed in a new window from which the timing diagrams can be obtained.
XTAS is started as follow:
XTAS
Upon entering this command the XTAS main window appears.
The file AvtTools/etc/Xtas allows modification of certain characteristics of the graphical interface. For example, the color and the size of the windows of xtas can be modified in this file.
The XTAS main desk window is the starting point for using XTAS. You can choose to use the menus or the buttons. Buttons are shortcuts giving the same results as a selection in the menus.
The Main window looks like:
The "Config" menu in XTAS provides access to a number of dialogs containing configuration options affecting the performance and appearance of the graphical database browser. These options are detailed in the following sections.
The memory size dialog allows the user to set the maximum and the current amount of memory used as the cache for loading delay and signal details. This dialog looks as follows:
This dialog box allows the user to add or remove Xtas' tool bar buttons. If a button is not checked, it does not appear in the Xtas' tool bar. The dialog also indicates which action corresponds to the button and in which menu this action is also available. In addition, the user can customize the button's bar by checking or not a button. This dialog appears as follows:
A similar dialog is available in the menu "Option" of other windows.
This dialog allows the user to choose between a graphical or textual display for the path or delay windows. The graphical display uses static text boxes and icons whereas the textual one displays information in plain text. The textual display is recommended for long signal names and long lists as it has faster display. This dialog appears as follows:
The textual display can be forced as default using the xtasTextualDisplay configuration variable.
After opening the XTAS main window you need to load a DTX format timing database. Choose open in the file menu of the XTAS main window.
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This button acts like a shortcut for the opening of the database. |
you will then be presented with the XTAS database request dialog. Choose which timing database to load by selecting it in this dialog.
The default filter can be changed using the xtasDatabaseFilter configuration variable.
It is also possible to load a CTX format timing database containing information given by crosstalk analysis (See chapter 'Output Files' of the HITAS Reference Guide for further information on this format).
To do this, you must select the timing database in DTX format in the XTAS database request dialog (change Filter to "*.dtx" to have access to the list of DTX files). Then, if a corresponding CTX file exists, the following dialog will appear asking confirmation to load it:
Choose exit in the File menu in order to close XTAS.
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Clicking this button in the main window will exit XTAS. In any other window, it will close the current window. |
Select Connectors in the View menu of the XTAS main window in order to open the XTAS connectors window
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This button opens the XTAS connectors window. |
The XTAS connector window allows viewing of the list of the connectors of the Instance. This list can be filtered according to name and/or hierarchical level.
Select Registers in the View menu of the XTAS main window in order to open the XTAS registers window
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This button opens the XTAS registers window. |
The XTAS registers window allows viewing of the list of the registers of the Instance. This list can be filtered according to name and/or hierarchical level.
Select Commands in the View menu of the XTAS main window in order to open the XTAS commands window
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This button opens the XTAS commands window. |
The XTAS commands window allows viewing of the list of the commands of the Instance. This list can be filtered according to name and/or hierarchical level.
Select Precharges in the View menu of the XTAS main window in order to open the XTAS precharges window
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This button opens the XTAS precharges window. |
The XTAS precharges window allows viewing of the list of the precharges of the Instance. This list can be filtered according to name and/or hierarchical level.
Select Break Points in the View menu of the XTAS main window in order to open the XTAS break points window
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This button opens the XTAS break points window. |
The XTAS break points window allows viewing of the list of the break points of the Instance. This list can be filtered according to name and/or hierarchical level.
Select Internal Signals in the View menu of the XTAS main window in order to open the XTAS all signals window
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This button opens the XTAS all signals window. |
The XTAS all signals window allows viewing of the list of all internal signals of the Instance. This list can be filtered according to name and/or hierarchical level.
Select Get Paths in the Tools menu of the XTAS main window in order to open the XTAS get paths window
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This button opens the XTAS get paths window. |
The XTAS get paths window allows the setting of numerous parameters. From these parameters XTAS will display the selected critical paths.
Select Get Delays in the Tools menu of the XTAS main window in order to open the XTAS get delay window
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This button opens the XTAS get delay window. |
The XTAS get delay window allows the setting of numerous parameters. From these parameters XTAS will display the selected max delays.
Select Stability in the Tools menu of the XTAS main window in order to open the XTAS stability parameterization window
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This button opens the XTAS stability parameterization window. |
The stability parameterization window allows you to specify the stability and/or crosstalk analysis options and then performs the analysis.
From any window in XTAS it is possible to identify the use and associated menu of any of the Xtas' tool bar buttons. To do this, open the XTAS Button Configuration window from the Options menu.
The following functions are available from most of the window types:
If the INF file has been modified during a XTAS session (for example for false path information), it is possible to reload it from the File menu.
This section describes timing signals browsing features. Example is given below for memory elements. Browsing of connectors, commands, precharges, break points and internal signals is done the same way.
Open the XTAS Registers window in order to display the memory elements.
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Clicking this button opens the XTAS registers window. |
The following options are available:
Signal Mask | You can give the name of a particular register in order to display this register. The '*' is a wildcard you can use to select a set of signals whose names will fit the conditions you have given. The default value is '*' and will display all the registers. |
Figure name | This is the name of the database you have load in XTAS |
Instance name | This is the name of the instance whose registers you are looking for. |
List | This option opens the Hierarchy window. It displays the hierarchy of the figure, and allows you to select another instance. It is possible to make the search through all levels. An On-Line help is available for this option in the hierarchy window. |
Items | You can set the number of registers you want to display in the Information Area. The resulting list will be given either in a single page or on several pages depending if the number of registers is greater than the value given. |
Search | Displays the registers in the Information Area. |
Signals List | If the number of register is greater than the figure for Item XTAS will give the registers list on several pages. The signals list allows you to access all the signals. If the number of register is inferior to the value given, there is only one page. |
After Search, this option shows information on a selected signal. |
The resulting XTAS Registers window of a Search looks like:
Double clicking on a register displays more information about that register in the XTAS Signals Info Window.
Open the XTAS Get Paths window in order to select options for displaying critical paths.
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Clicking this button opens the XTAS Get Paths window. |
The XTAS Get Paths window looks like:
This window is the first step to viewing the critical paths of the instance. Use the options to set criteria for displaying critical paths.
You can use the following options in the XTAS Get Paths window:
Start Text Box | |
This text box describes the regexp (including *) to be matched for the beginning signal of the path. The Start button permits browsing of path extremity signals in the loaded figure. | |
End Text Box | |
This text box describes the regexp (including *) to be matched for the terminating signal of the path. The End button permits browsing of path extremity signals in the loaded figure. | |
Clock(s) Text Box | |
This text box describes the regexp (including *) to be matched for the clock signal when viewing access. | |
Time Bounds | |
These text boxes indicate the time bounds between which paths must be found. | |
Request Type | |
Choose the search criteria. When choosing to view "Paths and Access" the "Clock(s)" text box becomes available. | |
Slopes Mask | |
Select here the desired types of transitions between the start signal and the end signal. | |
Max/Min | |
The Max button performs the search for the longest paths. The Min button performs the search for the shortest paths. | |
Order by | |
These buttons select the source signal of the paths search. In order to reduce computing time, the signal (start or end) with the most restrictive mask must be chosen. | |
Search Level | |
These text boxes allow limiting of the path search to certain levels of hierarchy. The List button allows selecting of instances. By default, search is performed in all levels of hierarchy. |
XTAS display the XTAS Critic Paths Window:
Each line in the window corresponds to a critical path. The name and transition of the path terminals are given, together with the path delay and output slope.
Near critical paths (or parallel paths) are paths with the same terminals as a critical path. Optimization of a critical path is often useless if parallel paths are not similarly optimized.
In the XTAS Critic Paths window open the XTAS Get Parallel Paths in order to view the near critical paths.
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Clicking this button opens the XTAS Get Parallel Paths window. |
The XTAS Get Parallel Paths window looks like:
This window is the first step to viewing the near critical paths.
The following options are available:
Signals Bounds | The On Path text box describes the regexp (including *) to be matched for intermediary signals of the parallel path. The On Path button permits browsing of signals in the loaded figure. |
Slopes Mask | Select here the desired type of selection of the intermediary
signal. Available types of selection are:
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Max/Min | The Max button performs the search for the longest paths. The Min button performs the search for the shortest paths. |
Order by | These buttons select the source signal of the paths search. In order to reduce computing time, the signal (start or end) with the most restrictive mask must be chosen. |
Time Bounds | These text boxes indicate the time bounds between which paths must be found. Only critical paths or all paths can be searched, by selecting or not the button Critical Paths. |
Search Level | These text boxes allow limiting of the path search to certain levels of hierarchy. The List button allows selecting instances. By default, search is performed in all levels of hierarchy. |
XTAS display the XTAS Parallel Paths Window:
If a DTX file has been generated, it is possible to display elementary gate or RC delays according to certain criteria.
In the XTAS Main window open the XTAS Get Delay window in order to view elementary delays.
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Clicking this button opens the XTAS Get delay window. |
The XTAS Get Delay window looks like:
The following options are available:
Start Text Box | This text box describes the regexp (including *) to be matched for the beginning signal of the path. The Start button permits browsing of path extremity signals in the loaded figure. |
End Text Box | This text box describes the regexp (including *) to be matched for the terminating signal of the path. The End button permits browsing of path extremity signals in the loaded figure. |
Slopes Mask | Select here the desired types of transitions between the start signal and the end signal. |
Max/Min | The Max button performs the search of the maximum delays. The Min button performs the search of the minimum delays. |
Order by | Those buttons select the type of delay to be searched. RC means interconnect delays, Gate means Gate delays. |
Time Bounds | Those text boxes indicate the time bounds between which paths must be found. Only critical paths or all paths can be searched, by selecting or not the button Critical Paths. |
Search Level | Those text boxes allow the search of paths in but chosen levels of hierarchy. The List button permits to select instances. By default, search is performed in all levels of hierarchy. |
Xtas display the Xtas Delay Max Window:
Each line in the window corresponds to an elementary delay or timing arc. The input and output transitions of the timing arc are given, as well as the delay and the output slope. The type icon identifies the delay as corresponding to a gate or RC interconnection.
When designers use an electrical simulator such as ELDO or HSPICE to obtain path timing information, the path must be extracted manually and appropriate stimuli provided. XTAS can automate this procedure for any identified path.
From the XTAS Path Detail window, it is possible to run a simulation with the electrical simulator of your choice. You need only to configure the simulation parameters. Path extraction and stimuli generation are automatic.
In a new XTAS Path Detail window, you can compare results given by HITAS with these given by the simulator.
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Clicking this button opens the XTAS Simulation Parameterization window. |
The XTAS Simulation Parameterization window looks like:
This window is the first step to simulate a path.
The following options are available:
Technology File | Click on the Open button to choose the directory of the technology file and select it in the list. This is equivalent to the avtTechnologyName configuration variable. |
Simulation Tool | Allows the user to choose the electrical simulator he wants to use and the corresponding command line. He can also specify the output format generated by the simulator and the file format for stdout redirection. It is equivalent to the simToolModel, the avtSpiceString, the avtSpiceOutFile and the avtSpiceStdoutFile configuration variables respectively. Checking the "Use Print" box allows getting an array of value for a node, it is equivalent to setting simUsePrint configuration variable to "yes". Checking the "Use Measure" box specify to extract value from waveform using combination of arithmetic expressions, it is equivalent to setting simUseMeasure configuration variable to "yes". |
Constraints | Allows the user to set the input/output constraints parameters for simulation. Specify the input slope start time and the transient time of the input slope in picoseconds. Specify the output capacitance value in Femto-farads. It is equivalent to the simInputStartTime and the simSlope and the simOutCapaValue configuration variables. |
Conditions | Allows the user to set the simulation conditions like the duration (in nanoseconds), the maximum voltage (in Volts) and the temperature (in degrees Celsius). It is equivalent to the simTransientTime, the simPowerSupply and the simTemperature configuration variables respectively. The user can also specify the spice options to be driven into the spice file for simulation it is equivalent to the simSpiceOptions configuration variable. |
Thresholds | Allows the user to set the thresholds of a slope as a percentage of VDD. It is equivalent to the simVth, the simVthHigh and the simVthLow configuration variables. |
Step | Allows the user to set the transient calculation step for the simulation in nanoseconds. Equivalent to the simTransientStep configuration variable. |
Xtas displays the Xtas Simulated Critic Max Path Detail Window:
For all timing arc data (Slope, Delay and Total) there are two columns:
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These columns give the values obtained with the static timing analysis. |
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These columns give the values obtained with the selected simulator. |
It is possible to view a graphical representation of a path.
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Clicking this button opens the XTAS Path Visualization window. |
The XTAS Path Visualization window looks like:
This window is the first step to visualize a path.
There are two modes of representation:
Highlight | displays all the circuit and highlights the selected path. |
Extract | displays only the selected path. |
Xtas displays the following window:
If a DTX file has been generated, it is possible to display elementary gate or RC delays according to certain criteria.
In the XTAS Main window open the XTAS Get Delay window in order to view elementary delays.
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Clicking this button opens the XTAS Get delay window. |
The XTAS Get Delay window looks like:
The following options are available:
Start Text Box | This text box describes the pattern (including *) to be matched for the beginning signal of the path. The Start button permits browsing of path extremity signals in the loaded figure. |
End Text Box | This text box describes the pattern (including *) to be matched for the terminating signal of the path. The End button permits browsing of path extremity signals in the loaded figure. |
Slopes Mask | Select here the desired types of transitions between the start signal and the end signal. |
Max/Min | The Max button performs the search of the maximum delays. The Min button performs the search of the minimum delays. |
Order by | Those buttons select the type of delay to be searched. RC means interconnect delays, Gate means Gate delays. |
Time Bounds | Those text boxes indicate the time bounds between which paths must be found. Only critical paths or all paths can be searched, by selecting or not the button Critical Paths. |
Search Level | Those text boxes allow the search of paths in but chosen levels of hierarchy. The List button permits to select instances. By default, search is performed in all levels of hierarchy. |
Xtas display the Xtas Delay Max Window:
Each line in the window corresponds to an elementary delay or timing arc. The input and output transitions of the timing arc are given, as well as the delay and the output slope. The type icon identifies the delay as corresponding to a gate or RC interconnection.
It is possible to launch the static timing analyzer with or without the crosstalk analysis from within XTas. In order to perform this analysis, it is first necessary to create a constraints file (.inf file). If this file exists alongside the timing database, then a single button launches the analysis after specifying a few options. Any violations are displayed in a new window from which the timing diagrams can be obtained and the noise analysis can be launched.
In the XTAS Main window open the XTAS in order to begin the static timing analysis.
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Clicking this button opens the XTAS Stability Parameterization window. |
The XTAS Stability Parameterization window looks like:
This window is the first step of the static timing analysis.
If static timing analysis has been performed on the current figure, the user can directly load the results from the .sto file.
The user can choose to perform the static timing analysis with full handling of crosstalk effects. If this box is checked, the user has access to the crosstalk analysis parameterization area. See the HITAS Reference Manual for more detailed explanations of the configuration options.
Crosstalk Analysis Type | |||||||||||||||||||||
In the "Remove Non-Aggression" mode, all aggression is assumed initially. In the "Detect Aggression" mode, no aggression is assumed initially. In addition to that mode, you can check the box "Observable Only" in order to have less pessimistic results. | |||||||||||||||||||||
No More Aggressions Stop Conditions | |||||||||||||||||||||
These are conditions for stopping slope recalculation when no further aggression is detected or removed: "Min Slope Change" represents the minimum significant slope variation in picoseconds (equivalent to the stbCtkMinSlopeChange configuration variable) and "Max Iteration Number" represents the maximum number of recalculation iterations (equivalent to the stbCtkMaxLastIter configuration variable). | |||||||||||||||||||||
Crosstalk Model | |||||||||||||||||||||
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Options | |||||||||||||||||||||
The crosstalk analysis can generate a report file (.ctk), which contains delay changes,
detailed aggression reports and noise estimation.
You can set lower limits to avoid reporting excessive information:
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Analysis type | The best case analysis is performed by assuming that in the initial conditions, latch transparency is at maximum. The worst case analysis is performed by assuming that in the initial conditions, there is no latch transparency. In Multi-Interval mode, all switching windows are maintained whereas in Mono-Interval mode, they are merged into a single interval for setup/hold verification. To perform the crosstalk analysis, the Mono-Interval mode is required. See HITAS Reference Guide for further information. |
Monophase Latch | In the Flip-Flop mode, a latch clocked on the same phase than the latch generating its input data is assumed to be a flip-flop. In the Transparent mode, a latch clocked on the same phase than the latch generating its input data is always transparent. In the Error mode, a latch clocked on the same phase than the latch generating is input data is not allowed, and an error is reported. See HITAS Reference Guide for further information. |
Level | In the All Levels mode, constraints are calculated using all paths throughout the hierarchy. In the Top Level mode, constraints are calculated using only the paths at the top level (i.e. the interconnections at the top level). |
Error Type | In the Setup mode, only errors due to setup time violations are reported. In the Hold mode, only errors due to hold time violations are reported |
Error Reports | In sto mode, a .sto file is driven. This file contains the switching windows of all the signals in the figure. In str mode, a .str file is driven. This contains the signals on which a setup or hold violation occurs. For each error on a signal, the corresponding origin signals are also reported. |
Error Report | The Error Margin is added to the hold and setup constraints of the figure. For example, if there is an error margin of 100ps, a signal with a setup or a hold time below 100ps will be reported as an error. |
Information File | Specification for the stability analysis can be loaded from information file. Click on the 'Open' button to choose this file. It is possible to merge information from several files. In that way, you have to select files one by one setting the 'Complete' option. If you want to erase all information to load a new one, choose the 'Replace' option. If the avtReadInformation File is set, no need to do this operation, unless you want to merge another information. About the information file see the chapter 'Input File' of the HITAS Reference Guide. |
After performing crosstalk analysis from within XTAS, all delays are subsequently given with crosstalk effect values (see HITAS Reference Guide for further information). To view these new delay values you have to open the critic path detail window (see section 'Viewing Path Details').
Any reference points for which the timing checks show errors re displayed in the static timing analysis results window.
In order to understand the violations, it is possible to display detailed timing diagrams for any terminal in the circuit.
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Click on this button to open the signal Selection dialog. |
Enter the name of any terminal in this dialog. If you selected a signal in the list of errors this signal is given by default. When you click on OK then XTAS displays the Debug... window.
The XTAS Debug window looks like:
The Input Signals List displays the input terminals of the paths which give rise to violations at the specified signal.
Selecting an input signal displays a timing diagram giving the signal switching windows of the path terminals as well as illustrating the required timing constraints.
Coupling capacitance has the effect of generating noise on signals. The Noise Analysis calculates upper and lower peak voltages on a signal as a result of any aggression due to crosstalk. Then XTAS displays the results of the analysis as a list of signals sorted according to the peak noise value.
The Noise Analysis needs to obtain information on aggressor and victim signals from memory. So Crosstalk Analysis must have been run from XTAS before launching the Noise Analysis. In the Static Timing Analysis Results window open the noise window in order to begin the Noise Analysis.
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Clicking this button opens the XTAS Noise Parameterization window. |
The XTAS Noise Parameterization window looks like:
This window is the first step of the noise analysis.
The user can configure the results display by giving the number of item he wants to view per page.
The Noise analysis results window looks like:
The results are displayed as a list of signals with their noise information. To check which signals present a risk of crosstalk errors, a score based place is performed. There are four criteria: one for the crosstalk impact and three for the probability the aggression occurs. Each of these criteria gives a mark on 10 points.
Each line of the results list gives the following information on the corresponding signal:
General Information | |
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Rise and Fall Peak Information | |
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Scores | |
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The user can find the same information in the Noise section of the Crosstalk Report (.ctk file). See HITAS Reference Guide for further information.
The user can sort the results on his favorite criterion by clicking on the corresponding button. The sort is always in descending order. The first five buttons from the right allows to sort on the corresponding score (Global, Noise, Interval, Crosstalk or Activity). The other criteria, based on the noise peak value, are the following:
Inside Alim Max | |
Signals are sorted on the maximum peak noise value, according to their level. This means that if the level of a signal is High, the selected peak noise value is the maximum fall peak noise value. If the level of a signal is Low, the selected peak noise value is the maximum rise peak noise value. | |
Inside Alim Real | |
Signals are sorted on the real peak noise value, according to their level. This means that if the level of a signal is High, the selected peak noise value is the real fall peak noise value. If the level of a signal is Low, the selected peak noise value is the real rise peak noise value. | |
Rise Peak Max | |
Signals are sorted on the maximum rise peak noise value, regardless of the static level. | |
Rise Peak Real | |
Signals are sorted on the real rise peak noise value, regardless of the static level. | |
Fall Peak Max | |
Signals are sorted on the maximum fall peak noise value, regardless of the static level. | |
Fall Peak Real | |
Signals are sorted on the real fall peak noise value, regardless of the static level. |
In the Noise Analysis Results window the user can configure the scores coefficients and minimum values.
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Clicking on this button opens the Scores Configuration window. |
The Scores Configuration window looks like:
This window allows the user to set two parameters for each score (Noise, Interval, Crosstalk and Activity). The first one is the weighting to compute the global score obtained by each signal. The second one is the minimum value required for the signal to be reported in the results list. These actions are equivalent to set the following configuration variables:
Noise | stbCtkCoefNoise and stbCtkMinNoise. |
Interval | stbCtkCoefInterval and stbCtkMinInterval. |
Crosstalk | stbCtkCoefCtk and stbCtkMinCtk. |
Activity | stbCtkCoefActivity and stbCtkMinActivity. |
In the Noise Analysis Results window the user can access crosstalk information.
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Selecting a signal and clicking on this button opens the Crosstalk Information window. |
The Crosstalk Information window looks like:
General | This part gives the signal state and its name. It gives also the ground capacitance and the total crosstalk capacitance on this signal. |
Noise | This part displays the electrical noise on the signal as it is specified in the Noise Analysis Results window (See previous section). Vth is the static threshold of the following gate. |
Aggressors List | This part gives the list of the signal aggressors. Each line
indicates the aggressor signal Name, its Net Name, the kind of influence it has
on the victim and the coupling capacitance on the victim due to this aggressor.
If the signal does not appear on the line, there is no corresponding timing signal. As no stability information is provided for this signal, the crosstalk engine assumes that this signal is always an active aggressor. If the character 'B' or 'W' or both are present on a line, this means that the aggressor can modify minimum propagation delays (B = Best Case) or maximum propagation delays (W = Worst Case). If the character 'R' or 'F' or both are present on a line, this means that the aggressor has made a contribution to calculate the real rise (R) peak noise value or the real fall (F) peak noise value. These characters can appear in lower case ('b','w','r','f') when crosstalk mutex are used. This means the influence of the signal is ignored because of the crosstalk mutex. Aggressors can be sorted by the signal name or by the capacitance value using the button at the top of the corresponding column. Successive press on the button sort alternatively in ascending or descending order. |