After the analysis is complete, the Noise window opens.
Click the links on the left side of the window to view different information about the SSN analysis. For example, click I/O Bank Details to view the following information:
- Displays the I/O banks available in the device. Each I/O bank has pin icons indicating how full the bank is. A check mark indicates a passing result, and a red circle indicates a failure.
- Displays the name of the user I/O in the FPGA design.
- I/O Std, VCCO, Slew, Drive Strength
- Displays the appropriate values for the port or bank.
- Off-Chip Termination
- Displays the default terminations for each I/O standard, if
one exists. Displays either None or a short description of the expected or
defined off-chip termination style. For example,
FP_VTT_50describes a far-end parallel 50 Ω termination to VTT termination style.
HSTL_1describes a far-end 40 Ω termination to VTT. The full list of termination styles is available in one of the following user guides, depending on your device.
- 7 Series FPGAs SelectIO Resources User Guide (UG471)
- UltraScale Architecture SelectIO Resources User Guide (UG571)
For LVTTL (at 2 mA, 4 mA, 6 mA, and 8 mA) no termination is assumed. However, for LVTTL (at 12 mA and 16 mA) a far-end parallel termination of 50Ω to VTT is assumed. As a result of this termination, the available noise margin is less for signals with drive strength of 12 mA, or more, when compared to 2 mA to 8 mA. 7 series devices, Zynq®-7000, and UltraScale™ devices use this assumption for applicable drive strengths.
To change the settings, use either of the following methods:
- Use the CSV file import feature described in Importing a CSV File.
- In the I/O Ports table, select an item from the drop-down list.
- Remaining Margin %
- Displays the amount of noise margin that is left over after accounting for all SSN in the bank.
- Displays information about the I/O bank or groups.