AR# 44394

PlanAhead, 7 Series - What does margin in SSN analysis mean?

Description

If I am targeting a 7 Series FPGA in the PlanAhead tool and performing SSN, how is the tool analyzing the amount of noise in the system compared to the ideal margin?

Solution

VDH (voltage drive high) - Vih min (voltage input high) =  the logic 1 ideal margin. 

Vil (voltage input low) - VDL (voltage drive low) = the logic 0 ideal margin. 

Using a hammer 101010 pattern at the resonant frequency, the noise at the far end of the line is measured for logic 1 and logic 0.

The limit is the number of I/Os that can switch and still have remaining margin. 

The remaining margin is the minimum of logic 1 ideal margin, logic1 noise, and logic 0 ideal margin, logic 0 noise.


 

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
31905 Simultaneously Switching Noise - Where can I find documentation on SSO/SSN? N/A N/A

Associated Answer Records

Answer Number Answer Title Version Found Version Resolved
47225 SelectIO Design Assistant - How to Terminate a Transmission Line N/A N/A
AR# 44394
Date 07/09/2018
Status Active
Type General Article
Tools