Main Content

Eye Measurement

Calculate metrics from eye diagram

Since R2024a

expand all in page
  • Eye measurement block

Libraries:
Mixed-Signal Blockset / Utilities
SerDes Toolbox / Utilities

Description

The Eye Measurement block generates eye pattern from time-domain waveform data and calculates metrics from the generated pattern.

Examples

expand all

This example uses:

Open Script

This example shows how to produce eye diagrams and related metrics for sampled data systems in Simulink.

Set Up Eye Measurement Block

Open the model eyeMeasurementInDFECDRExampleModel attached with this example. The model was originally created in the SerDes Designer app and then exported to Simulink®. For more information, see Design SerDes Systems and Export IBIS-AMI Models.

model = "eyeMeasurementInDFECDRExampleModel";
open_system(model);

In the eyeMeasurementInDFECDRExampleModel model, double-click on the Rx subsystem. Then right-click the DFECDR and select Look under mask to enter the DFECDR subsystem. Add an Eye Measurement block.

Note The Eye Measurement block is not supported for IBIS-AMI model generation. Remove the Eye Measurement block before exporting the model to IBIS-AMI.

Double-click on the Eye Measurement block to open its dialog.

Set the Configuration tab parameters to match the signal:

  • Set Enable threshold input port to on

  • Set Modulation to Modulation

  • Set Enable clock input port to on

  • Set Amplitude range to [-0.2, 0.2]

  • Set Hold off time to IgnoreBits and its unit to UI

  • Set Symbol time (s) to SymbolTime

  • Set Sample time (s) to SampleInterval

Modulation, IgnoreBits, SymbolTime, and SampleInterval are model properties controlled by the Configuration block in the top level of the model.

In the Eye Mask tab:

  • Set Eye mask type to Rectangular

  • Set W1 (UI) to 0.2

  • Set H to 0.1

In the Metric Setup tab:

  • Set Store results in base workspace to on

  • Set Result variable name to eyeResults

This saves the metrics to the base workspace in the variable named eyeResults once the simulation ends.

Apply the changes.

Connect Eye Measurement Block to DFECDR

Connect the data input of the Eye Measurement block to the output signal from the DFECDR. Add a Bus Selector block. Connect the input of the bus selector to the ClkAMI output port on the DFECDR. Use the Bus Selector to select the signal clockTime from the bus.

Connect the output port from the bus selector to the clock input port on the Eye Measurement block. Connect the PAM_Thresholds signal from the DFECDR to the thresholds input to the Eye Measurement block.

open_system(model + "/Rx/DFECDR", "force");

Run the simulation and confirm that the eye opening is centered, the correct number of unit intervals is visible, and that the dynamic range of the signal is fully within the diagram.

sim(model);

Export Metric Results

Once the simulation is complete, find the metric results in the base workspace.

disp(eyeResults);

         Metric          Position       Unit        SER     Extrapolation      Results   
    _________________    _________    _________    _____    _____________    ____________

    "Eye Height"         "0"          "Seconds"    1e-05       "None"        {1x1 struct}
    "Best Eye Height"    <missing>    "NaN"        1e-05       "None"        {1x1 struct}
    "Eye Mask Margin"    "NaN"        "NaN"        1e-05       "None"        {1x1 struct}

To retrieve the width and height margins, select the last element in the results column of the table, and from that structure retrieve the field named Margin.

eyeResults.Results{end}.Margin

ans =

    0.0062    0.0373

This example uses:

Open Script

This example shows how to produce eye diagrams and related metrics for specific signals in a SerDes system using the Eye Measurement block.

Set Up Constants

This example compares eye openings at three different signals in the model:

  1. The input to the receiver

  2. The output of the CTLE

  3. The output of the DFE

Open the model eyeMeasurementExampleModel_1Eye attached with this example. The model was originally created in the SerDes Designer app and then exported to Simulink®. For more information, see Design SerDes Systems and Export IBIS-AMI Models.

model = "eyeMeasurementExampleModel_1Eye";
open_system(model);

The Eye Measurement block does not have a phase detector or CDR, but the eye opening must be centered in the diagram for metric calculations to succeed. Use a manual phase offset to center the eye opening.

phaseOffset = 0.7; % UI

Measure Eye at DFE Output

In the eyeMeasurementExampleModel_1Eye model, double-click on the Rx subsystem. Add an Eye Measurement block.

Note Eye Measurement block is not supported for IBIS-AMI model generation. Remove the Eye Measurement block(s) before exporting the model to IBIS-AMI.

Double-click on the Eye Measurement block to open the Block Parameters dialog box.

Set the Configuration tab parameters to match the signal:

  • Set Enable threshold input port to off

  • Set Modulation to Modulation

  • Set Symbol thresholds to 0

  • Set Enable clock input port to off

  • Set Phase offset to phaseOffset and its unit to UI

  • Set Amplitude range to [-0.2, 0.2]

  • Set Hold off time to IgnoreBits and its unit to UI

  • Set Symbol time (s) to SymbolTime

  • Set Sample time (s) to SampleInterval

Modulation, IgnoreBits, SymbolTime, and SampleInterval are model properties controlled by the Configuration block in the top level of the model.

Apply the changes.

Connect the data input of the Eye Measurement block to the output signal from the DFECDR. Name the Eye Measurement block Eye 3: DFE.

open_system(model + "/Rx");

Run the simulation and confirm that the eye opening is centered, the correct number of unit intervals is visible, and that the dynamic range of the signal is fully within the diagram.

sim(model);

Measure Eye at CTLE Output

Copy the Eye Measurement block and paste the copy into the model. Rename the copy to Eye 2: CTLE. Connect its data input to the output of the CTLE.

Measure Eye at Receiver Input

Paste another copy of the Eye Measurement block and rename it to Eye 1: Channel. Connect its data input to the input to the CTLE.

bdclose(model);
model = "eyeMeasurementExampleModel_3Eye";
load_system(model);
open_system(model + "/Rx");

Running the simulation as-is produces errors when the Eye Measurement block connected to the CTLE input attempts to calculate its metrics because its eye is closed. To avoid this, double click on the block to open its dialog and change the following parameters:

In the Metric Setup tab, click on each metric and then click Remove Selected Metrics. You can shift-click to select multiple metrics.

Additionally, to fit the data in the eye diagram, in the Configuration tab set Amplitude range to [-0.5, 0.5].

Apply the changes.

Run the simulation. There will be a warning because Eye 1: Channel is measuring a closed eye.

s = warning("off", "shared_msblks_measurement:eye:BlockPathWarningWrapper");
sim(model);
warning(s);

Limitations

  • Eye Measurement block does not support rapid accelerator mode.

Ports

Input

expand all

Input data used to construct the eye pattern, specified as a scalar.

Data Types: double

Sampling clock signal for input data, specified as a scalar. Windows for the eye pattern are centered on the clock edges.

If you are using clock times at the clock port, new clock times must be within 1 UI of the current simulation time. Clock times should occur in the center of the corresponding eye opening.

Dependencies

To enable this port, select the Enable clock input port in the Configuration tab.

Data Types: double

Symbol threshold(s), used to separate symbols when building the eye diagram. If you provide this information, it increases the robustness of the PAMn metrics.

If the data at the thresholds port is a vector, the same vector is used across all time points during measurements. If the data at the thresholds port is a matrix, the block uses one vector for each time point.

Dependencies

To enable this port, select the Enable threshold input port in the Configuration tab.

Data Types: double

Parameters

expand all

To edit block parameters interactively, use the Property Inspector. From the Simulink® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Configuration

Select to enable the threshold input port. By default, this port is enabled.

Number of symbol levels expected in the eye diagram, specified as a nonnegative integer scalar.

Programmatic Use

Block parameter: Modulation
Type: character vector
Values: nonnegative integer scalar
Default: 2

Select to enable the clock input port. By default, this port is enabled.

Determine how to sample waveform clock signals:

  • Rising — Sample the data waveform at the rising edge of the clock waveform.

  • Falling — Sample the data waveform at the falling edge of the clock waveform.

  • Both — Sample the data waveform at both rising and falling edges of the clock waveform.

  • Times — Sample the data waveform at the time values specified by the clock signal.

Programmatic Use

Block parameter: ClockType
Type: character vector
Values: Rising | Falling | Both | Times
Default: Rising

Edge detection threshold for waveform clocks, specified as a real scalar.

Dependencies

To enable this parameter, set the Enable clock input port option as on and set the Clock type as Rising, Falling, or Both.

Programmatic Use

Block parameter: ClockThreshold
Type: character vector
Values: real scalar
Default: 0

Represent how data is captured by the recovered clock from the system perspective.

  • Clocked — The data is captured at the input to the decision latch using the clock from the output of the clock recovery circuit.

  • Ideal — The data and clock are captured using an ideal reference clock source.

  • Convolved — The data eye and clock PDF captured in normal mode are convolved together to present an eye and clock that look as though the simulation had been run in clocked mode.

For more information, see Clock Modes (Signal Integrity Toolbox).

Note

If you set the Enable clock input port option as off, Clock mode is set to Ideal and you cannot change it.

Programmatic Use

Block parameter: ClockMode
Type: character vector
Values: Clocked | Ideal | Convolved
Default: Clocked

Delay between the clock edge and the timing origin, specified as a nonnegative real scalar in seconds, samples, or UI.

Note

Phase offset delay must be causal.

Programmatic Use

Block parameter: PhaseOffset
Type: character vector
Values: nonnegative real scalar
Default: 0

The width of the eye diagram in symbols, specified as a scalar.

Programmatic Use

Block parameter: SymbolsperDiagram
Type: character vector
Values: scalar
Default: 2

Minimum and maximum amplitudes contained in the eye diagram, specified as a two-element vector.

Programmatic Use

Block parameter: AmplitudeRange
Type: character vector
Values: two-element vector
Default: []

Number of amplitude bins in the eye diagram, specified as a positive integer scalar.

Programmatic Use

Block parameter: AmplitudeBins
Type: character vector
Values: positive integer scalar
Default: 257

Number of time bins in the eye diagram, specified as a positive integer scalar.

Programmatic Use

Block parameter: TimeBins
Type: character vector
Values: positive integer scalar
Default: 256

Delays measurement analysis to avoid corruption by transients, specified as a nonnegative real scalar in seconds, samples, or UI.

Programmatic Use

Block parameter: HoldOffTime
Type: character vector
Values: nonnegative real scalar
Default: 0

Time for one symbol, specified as a positive real scalar.

Note

Symbol time must be evenly divisible by Sample time.

Programmatic Use

Block parameter: SymbolTime
Type: character vector
Values: positive real scalar
Default: 16e-9

Time for one sample, specified as a positive real scalar.

If Sample time is specified as a 2- element vector, it represents the fixed-step discrete sample time in Simulink.

If Sample time is specified as a scalar, it represents the sample interval used in the SerDes Toolbox™.

Note

Symbol time must be evenly divisible by Sample time.

Programmatic Use

Block parameter: SampleTime
Type: character vector
Values: two-element vector | scalar
Default: [1e-9, 0]

Metric Setup

Click to add new eye diagram metric to calculate. You can define which metric to calculate at what point, the symbol error rate, and the extrapolation method.

Click to remove selected eye diagram metrics to focus on the area of interest.

Select to store the metric calculation result to the base workspace at the end of simulation.

Name of the metrics variable that stores measurement results in the base workspace.

Programmatic Use

Block parameter: MetricsVariableName
Type: character vector
Values: string
Default: ans

Click to export the simulation results to a file to save for later use.

Click to export the simulation results to the base workspace.

Eye Mask

Shape of the eye mask for the mask margin measurement. For more information, see eyeMask.

The width of the rectangle or diamond eye masks or the width at the center of the hexagon eye mask, specified as a positive real scalar.

Dependencies

To enable this parameter, set Eye mask type to Rectangle, Diamond, or Hexagon.

Programmatic Use

Block parameter: W1
Type: character vector
Values: positive real scalar
Default: 0.2

The width at the top and bottom of the hexagon eye mask, specified as a positive real scalar.

Dependencies

To enable this parameter, set Eye mask type to Hexagon.

Programmatic Use

Block parameter: W2
Type: character vector
Values: positive real scalar
Default: 0.1

The height of the rectangle, diamond or hexagon eye masks, specified as a positive real scalar.

Dependencies

To enable this parameter, set Eye mask type to Rectangle, Diamond, or Hexagon.

Programmatic Use

Block parameter: H
Type: character vector
Values: positive real scalar
Default: 0.1

Define the position of origin of the shape of the mask in the eye diagram. You can position it at the clock, or for the best eye height or width.

Dependencies

To enable this parameter, set Eye mask type to Rectangle, Diamond, or Hexagon.

Programmatic Use

Block parameter: PositionMaskInEye
Type: character vector
Values: At clock | For best height margin | For best width margin
Default: At clock

Define a custom eye mask from an eye mask object.

Dependencies

To enable this parameter, set Eye mask type to Custom.

Programmatic Use

Block parameter: CustomEyeMask
Type: character vector
Values: object
Default: []

Symbol error rate at which the block measures the eye mask margin, specified as a nonnegative real scalar in the range [0,1].

Dependencies

To enable this parameter, set Eye mask type to Rectangle, Diamond, Hexagon, or Custom.

Programmatic Use

Block parameter: MarginSER
Type: character vector
Values: nonnegative real scalar in the range [0,1]
Default: 1e-5

Extrapolation method to generate eye contours used for measuring eye margins.

Dependencies

To enable this parameter, set Eye mask type to Rectangle, Diamond, Hexagon, or Custom.

Programmatic Use

Block parameter: MarginExtrapolation
Type: character vector
Values: None | DualDirac
Default:

Name of the mask variable to export the mask to the base workspace.

Programmatic Use

Block parameter: MaskVariableName
Type: character vector
Values: string
Default: ans

Click to export the mask to a file to save for later use.

Click to export the mask to the base workspace.

Plot Setup

Select to automatically show the simulation results as plots at the end of simulation. You can define which type of plot to generate, including the eye, clock, and bathtub.

Define how the plots are grouped together.

Click to add new plot to show.

Click to remove selected plots to focus on the area of interest.

Click to show the plots.

More About

expand all

Version History

Introduced in R2024a

See Also

| |