To analyze the margin of a given link, it can be helpful to run multiple scans of the link with different MGT settings. This helps determine which settings are the best. The Vivado serial I/O analyzer feature enables you to define, run, save, and recall link sweeps, which are a collection of link scans.
A sweep runs on a link. To create a sweep, select a link in the Link window, and either right-click and choose Create Sweep, or click the Create Sweep button in the Link window toolbar. This brings up the Create Sweep dialog box, which looks similar to the Create Scan dialog box, except that it has additional options for defining which properties to sweep, and how.
| Sweep Setting | Description |
|---|---|
| Description | A user-defined name for the sweep. |
| Scan Type | The type of scan to run. This can be a 2D Eyescan or a 1D Bathtub plot. |
| Horizontal Increment | Allows you to scan the eye at a reduced resolution, but at increased speed by skipping horizontal codes. |
| Horizontal Range | Reducing the horizontal range increases the scan speed. By default, the entire eye is scanned (-1/2 of a unit interval to +1/2 in reference to the center of the eye). |
| Vertical Increment | Allows the user to choose to scan the eye at a reduced resolution, but increased speed by skipping vertical codes. |
| Vertical Range | Reducing the vertical range increases the scan speed. By default, the entire eye is scanned. |
| Dwell BER | Each point in the chart is scanned for a certain amount of time. Dwell BER allows you to choose the scan depth by selecting the desired Bit Error Ratio (BER). |
| Dwell Time | Dwell Time allows you to choose the scan depth by inputting the desired time in seconds. |
| Sweep Mode | The type of sweep to run. The choices are Semi Custom, Full Custom, and Exhaustive. |
After these settings are chosen, the next step is to choose the Sweep Properties. Any writable properties of the link can be swept. To add a property, click the "+" button on the left to add another row to the table. Click the Property Name to choose a property to sweep.
To change the values, click the Values to Sweep Cell, and use the chooser to select which values to sweep. If the property does not have enumerated values, type one hex value on each line of the text area provided.
- In the Semi Custom case shown in the following figure, every combination of the properties chosen is defined for a single scan, and that scan is performed according to the sweep properties. The number of sweeps that are performed, and in what order can be previewed by selecting the Preview & Scans tab.
- In the Full Custom case, the first choice for each of the properties
listed is used for the first scan, the second choice for each of the properties is
used for the second scan, etc. If one of the properties has fewer choices than other
properties, the last choice is used for all subsequent scans. With the same
properties choices but Full Custom as the sweep Mode, only three scans would be
performed.Figure 3. Sweep Properties Dialog Box
- In the Exhaustive case, the Values to Sweep is no longer editable, as all values are chosen for a given property.
When all the properties are set, to run each of the scans sequentially, keep Run Sweep checked. The list of scans is elaborated in the Scan window once you click OK.
During the sweep, the progress is tracked in the Scan window, and the latest Scan result is displayed.