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Quartus II and MAX7000S unused pins

I want the unused pins on my EPM7128S to be inputs so I can ground them.

After compiling my project, in the pin out file, all unused pins show up as GND* = "Unused I/O pin. This pin can either be left unconnected or connected to GND. Connecting this pin to GND will improve the device's immunity to noise."

That's what I want, however, under Assignments (menu) / Device (menu option) / Device & pin options (button) / Unused pins (tab) - I am concerned that "reserve all unused pins" is set to "as outputs that drive an unspecified signal" which seems to be the defualt. Does this setting get overridden?

Reply to
Andrew Holme
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snipped-for-privacy@hotmail.com (Andrew Holme) wrote

More info: Clicking OK on the "unused pins" tab adds a set_global_assignment

-name reserve_all_unused_pins command to the "fitter assignments" section of the .QSF file. This assignment was not there before. After recompiling, the unused pins were listed as RESERVED. The only way I've found to get the project options back to their original state is to delete the set_global_assignment command using Notepad. Is there a way to do it using the GUI?

The default fitter behaviour (i.e. GND*) and the default setting displayed by the GUI (output driving an unspecified signal) are inconsistent when the global assignment does not exist.

Reply to
Andrew Holme

Hi Andrew,

The setting is not overridden. The pins will remain unconnected in the hardware. MAX 7KS does not support Programmable Ground for IO pins. You could have been confused when you saw Quartus reporting those pins being set to GND*. GND* refers to the pin being either set to GND or NC. We will fix the report to reflect these pins as RESERVED

This refers to the confusion in the Quartus report. The GND* and the 'output driving an unspecific signal' are actually the same in MAX 7KS ie these unused pins remains unconnected in MAX 7KS.

If an assignment is not seen in the .qsf, it means that the assignment is set to a default value in Quartus. Whenever an assignment is changed via the UI, the assignment is written to the .qsf and remain even if the assigment is reset back to its default. Once a assignment is changed it is always stored in the qsf, even when it is changed back to a default value.

Hope this helps.

- Subroto Datta

Altera Corp.

Reply to
Subroto Datta

[snip]

Thanks. Actually, I'm still a bit confused. I've done my PCB board layout on the assumption unused pins are inputs. Most are ground. One or two are tied to +5V for convenience. These MUST be inputs!

It seems I have 3 choices with the unused pin setting:

  1. Set as reserved input
  2. Set as reserved output driving an unspecific signal
  3. Leave as default

Options 3 sounds a bit risky because you said GND* was the same as 2. So I MUST reserve them as inputs. Correct?

Reply to
Andrew Holme

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