Description

How do I capture a receiver eye diagram for the Speedster7t AC7t1500 SerDes using ACE?

Answer

An eye diagram can be captured for either PAM4 or NRZ. First, to receive the optimized eye shape, it is required to complete receiver equalization, or simply run the built-in self test (BIST), before capturing the eye diagram.

Method 1 (Tcl Commands):

For the data collection, read samples after the FFE, enter the following commands for capturing PAM4 in the ACE Tcl console:

cmd> jtag::capture_serdes_diagram_data <jtag_id> &ly;subsystem> <serdes_quad> <serdes_lane> [-output_file <string>] [-num_samples <int> (default: 500)] [-capture_point <string> (default: FFE)]
cmd> jtag::plot_serdes_diagram_data_matlab <input_file> <diagram_type> <mod> <figure_name> <figure_number> <rate>

For example:

cmd> jtag::capture_serdes_diagram_data $jtag_id ETHERNET_0 SERDES_0 0 -output_file {G:/path_to_data_dump/my_ffe_output.txt}
cmd> jtag::plot_serdes_diagram_data_matlab {G:/path_to_data_dump/my_ffe_output.txt} eye PAM4 my_plot 1 53.125Gbps

After the last command, wait for a few moments while the data is processed and the eye diagram appears in a popup window. If capturing data for NRZ mode, change PAM4 to NRZ in the above command line. Below are example eye diagrams of PAM4 and NRZ respectively.

Figure: Eye Diagram of PAM4

Figure: Eye Diagram of NRZ

Method 2 (ACE GUI)

It is also possible to use the ACE GUI to plot the eye diagram using the following simple steps:

1. Open an ACE project containing the I/O ring design configuration, and switch to the IP Configuration perspective.

2. Open a valid JTAG connection to the FPGA using the JTAG Tcl commands in the Tcl Console view (refer to the ACE User Guide):

   set jtag_id "AC12345"
   jtag::open $jtag_id
   jtag::ac7t1500_initialize_fcu $jtag_id

3. With an open JTAG connection, right-click any configured (green) SerDes lane in the I/O Layout Diagram view and select Plot SerDes Diagram:

    

   

   Figure: Plot SerDes Diagram Lane Selection Example

    

4. Configure the diagram plotting options in the Plot Serdes Diagram dialog and then click Finish:

    

   

   Figure: Plot SerDes Diagram Dialog Configuration Example

Note:

• Multiple diagrams can be plotted from the same capture data file using the jtag::plot_serdes_diagram_data_matlab Tcl command after completing these steps.
• The diagram plotting capture over JTAG takes a long time. For 500 samples, it typically takes upwards of 10 minutes to run.
• Remember to close the Eye Diagram after analysis to complete the Tcl session.