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Altera_Forum
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14 years ago

SSN and reserve pins as ground

Hi everyone, I started doing SSN analysis on my preliminary designs and I found that I had problems with my standard PCI signals (3.0V) creating SSN on other 3.0V I/Os and vice versa. I tr...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

Basically, I want to optimize my pinout in order to minimize SSN issues. I have two 3V-banks to drive PCI pins and other GPIOs. No matter what setting I use, even with SSN optimization, the fitter is not able to give me a suitable pinout with regards to SSN.

Basically, I don't assign 3V GPIOs and I let the fitter decide where to place them according to SSN optimization. But I still get SSN errors.

If I manually place some pins (like PCI_AD) and set a "ground" barrier using reserved pins, I can optimize the SSN and I get almost 0 errors for normal GPIOs. However, I'll get SSN errors for the reserved pinds that are connected to ground.