1.5. SSN Analysis Overview
Start SSN analysis early in the design cycle to obtain preliminary results and adjust your I/O assignments. Iterate through the design cycle to finally perform a fully constrained SSN analysis with complete information about your board.
The early pin-out flow assumes conservative design rules initially, and then lets you analyze the design and iteratively apply tighter design rules until SSN analysis indicates your design meets SSN constraints. You must define pass criteria for SSN analysis as a percentage of signal margin in both the early pin-out flow and the final pin-out flow. The pass criteria you define is specific to your design requirements. For example, a pass criterion you might define is a condition that verifies you have sufficient SSN margins in your design. You may require that the acceptable voltage noise on a pin must be below 70% of the voltage level for that pin. The pass criteria for the early-pin out flow may be higher than the final pin-out flow criteria, so that you do not spend too much time optimizing the on-FPGA portions of your design when the SSN metrics for the design may improve after the design is fully specified.
Did you find the information on this page useful?