To analyze the margin of a given link, it is often helpful to run a scan of the link using the specialized Eye Scan hardware of the Xilinx 7 series FPGA transceivers. The Vivado serial I/O analyzer feature enables you to define, run, save, and recall link scans.
A scan runs on a link. To create a scan, select a link in the Link window, and either right-click and choose Create Scan, or click the Create Scan button in the Link window toolbar. This brings up the Create Scan dialog (see the following figure). The Create Scan dialog shows the settings for performing a scan, as shown in the following table.
There are two types of scans that can be generated, the 2D Eyescan or the 1D Bathtub Plot. Both these scans use the same settings specified in the Create Scan dialog shown below. The Scan type field in the dialog below determines the type of scan generated.
|Description||A user-defined name for the scan.|
|Scan Type||The type of scan to run. This can be a 2D Eyescan or a 1D Bathtub plot.|
|Horizontal Increment||Allows you to choose 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 you 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.|
Dwell Time allows you to choose the scan depth by inputting the desired time in seconds.
The Dwell time setting is not supported on designs that use In System IBERT IP.
By default, the scan is run after it is created. If you do not want to run the scan, and only define it, uncheck the Run Scan check box.
If a scan is created, but not run, it can be subsequently run or run by right-clicking on a scan in the Scans window and choosing Run Scan (see the following figure). While a scan is running, it can be prematurely stopped by right-clicking on a scan and choosing Stop Scan, or clicking the Stop Scan button in the Scans window toolbar.