Eye Measurement
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
Measure Eye Openings in Simulink
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 toUI
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
Measure Eye Openings from Intermediate Signals in SerDes System Model
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:
The input to the receiver
The output of the CTLE
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 toUI
Set Amplitude range to
[-0.2, 0.2]
Set Hold off time to
IgnoreBits
and its unit toUI
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
data — Input data
scalar
Input data used to construct the eye pattern, specified as a scalar.
Data Types: double
clock — Sampling clock for input data
scalar
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
thresholds — Symbol thresholds used to separate symbols
vector | matrix
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
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
Enable threshold input port — Enable threshold input port
on (default) | off
Select to enable the threshold input port. By default, this port is enabled.
Modulation — Number of symbol levels in eye diagram
2
(default) | nonnegative integer scalar
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 |
Enable clock input port — Enable clock input port
on (default) | off
Select to enable the clock input port. By default, this port is enabled.
Clock type — Determine how to sample waveform clock signal
Rising
(default) | Falling
| Both
| Times
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 |
Clock threshold — Edge detection threshold for waveform clocks
0
(default) | real scalar
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 |
Clock mode — Represent how data is captured by recovered clock
Clocked
(default) | Ideal
| Convolved
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 |
Phase offset — Delay between clock edge and timing origin
0
(default) | nonnegative real scalar
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 |
Symbols per diagram — Width of eye diagram in symbols
2
(default) | scalar
The width of the eye diagram in symbols, specified as a scalar.
Programmatic Use
Block parameter:
SymbolsperDiagram |
Type: character vector |
Values: scalar |
Default:
2 |
Amplitude range — Minimum and maximum eye amplitudes in eye diagram
[]
(default) | two-element vector
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:
[] |
Amplitude bins — Number of amplitude bins in eye diagram
257
(default) | positive integer scalar
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 |
Time bins — Number of time bins in eye diagram
256
(default) | positive integer scalar
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 |
Hold off time — Delay before measurement analysis
0
(default) | nonnegative real scalar
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 |
Symbol time — Time for one symbol
16e-9
(default) | positive real scalar
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 |
Sample time — Time for one sample
[1e-9, 0]
(default) | two-element vector | scalar
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
Add Metric — Add new metric to calculate
button
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.
Remove Selected Metrics — Remove selected metrics
button
Click to remove selected eye diagram metrics to focus on the area of interest.
Store results in base workspace — Store metric results to base workspace
off (default) | on
Select to store the metric calculation result to the base workspace at the end of simulation.
Metrics variable name — Name of metrics variable that stores measurement results
ans
(default) | string
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 |
Export to file — Export simulation results to file
button
Click to export the simulation results to a file to save for later use.
Export to base workspace — Export simulation results to base workspace
button
Click to export the simulation results to the base workspace.
Eye Mask
Eye mask type — Shape of eye mask
Off
(default) | Rectangle
| Diamond
| Hexagon
| Custom
Shape of the eye mask for the mask margin measurement. For more information, see
eyeMask
.
W1 (UI) — Width of rectangle, diamond, and center of hexagon eye masks
0.2
(default) | positive real scalar
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 |
W2 (UI) — Width of top and bottom of hexagon eye mask
0.1
(default) | positive real scalar
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 |
H — Height of rectangle, diamond, or hexagon eye masks
0.1
(default) | positive real scalar
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 |
Position mask in eye — Position of origin of shape of mask in eye diagram
At clock
(default) | For best height margin
| For best width margin
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 |
Custom eye mask — Define custom eye mask from eye mask object
[]
(default) | object
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:
[] |
Margin SER — Symbol error rate to measure eye mask margin
1e-5
| nonnegative real scalar in the range [0,1]
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 |
Margin extrapolation — Extrapolation method to generate eye contours
None
(default) | DualDirac
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: |
Mask variable name — Name of mask variable to export mask
ans
(default) | string
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 |
Export mask to file — Export mask to file
button
Click to export the mask to a file to save for later use.
Export mask to base workspace — Export mask to base workspace
button
Click to export the mask to the base workspace.
Plot Setup
Show plots at end of simulation — Automatically show plots at end of simulation
on (default) | off
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.
Plot grouping — define how plots are grouped together
Subplot on same figure
(default) | One figure per plot
Define how the plots are grouped together.
Add Plot — Add new plot to show
button
Click to add new plot to show.
Remove Selected Plots — Remove selected plots
button
Click to remove selected plots to focus on the area of interest.
Show Plots — Show plots
button
Click to show the plots.
More About
Extrapolation
Extrapolation method is used to constitute the relation between specific SER values and the shape of the 2-D histogram. It is the core technology behind the generation of bathtub plots and eye contours.
During extrapolation method, the data is pre-processed, usually one symbol at a time on only a 1D slice of the said symbol.
The None
extrapolation method is a previous neighbor
interpolation of the cumulative sum an eye slice. For horizontal eye slices, the
extrapolation uses the timing origins. For vertical eye slices, the extrapolation uses the
symbol thresholds.
When moving outward from the center of the eye, it is a previous neighbor interpolation. When moving across the eye from one side to the other, it appears as a next neighbor interpolation that switches to a previous neighbor interpolation as you pass the center of the eye. This way, the result for a symbol error rate is a conservative estimate from the perspective of the eye opening, based on the data.
The Dual-Dirac
extrapolation algorithm first fits the
Dual-Dirac PDF to a column of the split histogram. Then it uses those coefficients to
calculate the inverse Dual-Dirac CDF for the specified SER(s). It is only applicable to
systems with an exponential impulse response whose time constant is on the order of the time
for one symbol, or less. The algorithm is also significantly slower that the None
extrapolation method.
Version History
Introduced in R2024a
See Also
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