N.C. pins, Not Connect pins

[Altera_Forum]

Can the N.C. pins be connected to GND or Vcc? 

I need to do this to make EPM3256 footprint compatible with EPM3512.

[Altera_Forum]

seems like it should be safe: 

 http://www.altera.com/support/kdb/solutions/rd03132006_933.html

[Altera_Forum]

However, this "explanation" (for a S-III) makes it more complicated than it needs to be: 

 http://www.altera.com/literature/dp/stx3/pcg-01004.pdf  This document lists N.C. as:   --- Quote Start ---  Do not drive signals into these pins.   When designing for device migration these pins may be connected to power, ground, or a signal trace depending on the pin assignment of the devices selected for migration. However, if device migration is not a concern leave these pins floating.  --- Quote End ---  That's not much help...   N.C. is a very abused term these days. It use to mean "No Connection", meaning that there was no internal connection to the electronics of the chip. These pins could be used for heat conduction, to make routing other pins easier, preparing for future chip upgrades, or just on a whim.   Recently I have seen pins marked "N.C." on the data-sheet internally connected to a disable on a switching power-supply, and vcc on a flash memory. In both of these cases, grounding the "N.C." pins caused rather severe problems.   Another data sheet listed N.C. as   --- Quote Start ---  No Connection. These pins must be connected to ground.  --- Quote End ---   ... What!?  I thought Altera was being helpful when they listed two types of pins on the S-III, N.C. and DNU (Do Not Use). After reading the document above, I went back to my schematic/artwork and floated all the N.C. pins.  Not a lot of help here, I know. But this is me renewing my call to those in charge of such things... [tirade] Don't just scatter N.C. around if you're getting bored. If it is not a N.C. pin, call it something else! There are lots of good names available, like Vcc, Gnd, disable, DNU, etc. Use the name that matches the pin's purpose! Leave N.C. for those pins that have *No Connection* inside the chip![/tirade]

[Altera_Forum]

Thank you for your reply. 

 Another document:   PCG-01012.pdf   says:     Do not connect these pins to any signal. These pins must be left unconnected.     and this is for MAX V devices. I supose that it is the same for MAX3000 devices because they are older.

[Altera_Forum]

i agree with donq, there is too much conflicting information. that solution should be modified to reflect NC behavior on all families

[Altera_Forum]

Just compile the design. 

Quartus will produce a .pin file which tells you exactly what to do with each pin.

[Altera_Forum]

The point being... 

 If you look one place it will tell you one thing. If you look somewhere else, it will tell you something else.  The pin file tells you "exactly" one thing, several PDFs tell you "exactly" something else.  Which one do you believe? Flip a coin? Eeny meeny? Should you just decide what you want the answer to be and look around till you find the explanation that fits?   It is a support staffs dream come true. If anyone ever has a problem connecting it up wrong, just find an example of the contradictory "explanation", then blame it on the user and blow them off.  Then the enablers will come along and tell you that there never was really any problem at all. "Just read this one document and ignore all the others."  Not really the best way to get things fixed.

[Altera_Forum]

It looks conflicting/complicated because there are different families and different use cases. 

 For example, take from the Stratix III guidelines you quoted. It may sound complicated but it really comes down to this: In a given package there are some pins that will be NC (not connected do the die) in some devices but in bigger devices will be connected to the die (Vcc, GND, VREF, etc). The guidelines say that if you're don't intent to migrate to a bigger device, you SHOULD (not MUST) leva NCs unconnected. However, if you intent to migrate to a bigger device, you MUST connect those pins properly.  On the other hand, the MAX V guidelines FCORDOBES quoted say you MUST leave NC pins unconnected. It's a stronger statement that the one in the Stratix III guidelines but different families have different guidelines. And I think none of MAX V packages actually has NC pins...  The .pin report is, however, case specific. For your combination of device family, package, intended migration devices, unused pin options, etc, it will tell you exactly what pin will be for your case.  Which only leaves one question: what to do with the NC pins that show up in the .pin report? There isn't nice guideline document for older families like MAX3000, but you can leave them floating.

[Altera_Forum]

OK, Thank you for all of your answers. 

I have taken a decision. I am going to put four jumpers connected between the N.C. pins and GND or Vcc (as each corresponds) for EPM3256 device (leaving them open). And if I want (or need) to use EPM3512 device I will only have to solder the two pins of each jumper to make the proper connection.   Thank you. FC.

[Altera_Forum]

Chips are designed by one team, datasheets and appnotes are written by another one and support is provided by yet another one. Naturally there are miscommunications in between. Thus the differences in recommendations. And it's made even worse by some companies explicitly concealing important design-related data that they treat as "intellectual property". 

Well, I guess we simply have to deal with it by acquiring experience with particular component families and knowing their shortcomings.

[Altera_Forum]

--- Quote Start ---  I have taken a decision. I am going to put four jumpers connected between the N.C. pins and GND or Vcc (as each corresponds) for EPM3256 device (leaving them open). And if I want (or need) to use EPM3512 device I will only have to solder the two pins of each jumper to make the proper connection.  --- Quote End ---    Which package are you using, by the way?