Assigning unused pins in Quartus II

Hi folks

I have a VHDL design which I'm putting on an FPGA with Quartus II.
There is a specific pin on the FPGA which I need to drive high. This
pin has no corresponding port in my VHDL file and I don't want to edit
the VHDL file.

I can find the option in Quartus to assign all unused pins to say
"driving low." However I want to keep the default at "driving low"
while assigning just this pin to "driving high."

The reason for this is that the default drving low value causes the
configuration controller on my dev-kit (NiosII Stratix kit) to
reconfigure repeatedly.

How can I assign just one pin to drive high? I'm certain it can be
done, but for the life of me I cannot find the option in Quartus.

Thanks in advance,
Richard

rnbrady wrote:
> I have a VHDL design which I'm putting on an FPGA with Quartus II.
> There is a specific pin on the FPGA which I need to drive high. This
> pin has no corresponding port in my VHDL file and I don't want to edit
> the VHDL file.
>
> I can find the option in Quartus to assign all unused pins to say
> "driving low." However I want to keep the default at "driving low"
> while assigning just this pin to "driving high."

This is one of the most mind boggling things about Quartus II.  By
default it set all unspecified pins to ground, which is a terrible
default as one quick first test is likely to miss this and will end up
driving ground to a bunch of should-be input pins.

Richard, the fix for you problem is (from memory) to enter the general
settings (assignments?) and change the pin default from "output driving
ground" to "input tristated".  That should solve this problem
completely.

Tommy


>
> The reason for this is that the default drving low value causes the
> configuration controller on my dev-kit (NiosII Stratix kit) to
> reconfigure repeatedly.
>
> How can I assign just one pin to drive high? I'm certain it can be
> done, but for the life of me I cannot find the option in Quartus.
> 
> Thanks in advance,
> Richard

The Unused Pin Option setting is in: Assignments
Settings->Device->Device & Pin Options->Unused Pins.

Hope this helps,
Subroto Datta
Altera Corp.

Tommy Thorn wrote:
> rnbrady wrote:
> > I have a VHDL design which I'm putting on an FPGA with Quartus II.
> > There is a specific pin on the FPGA which I need to drive high. This
> > pin has no corresponding port in my VHDL file and I don't want to edit
> > the VHDL file.
> >
> > I can find the option in Quartus to assign all unused pins to say
> > "driving low." However I want to keep the default at "driving low"
> > while assigning just this pin to "driving high."
>
> This is one of the most mind boggling things about Quartus II.  By
> default it set all unspecified pins to ground, which is a terrible
> default as one quick first test is likely to miss this and will end up
> driving ground to a bunch of should-be input pins.
>
> Richard, the fix for you problem is (from memory) to enter the general
> settings (assignments?) and change the pin default from "output driving
> ground" to "input tristated".  That should solve this problem
> completely.
>
> Tommy
>
>
> >
> > The reason for this is that the default drving low value causes the
> > configuration controller on my dev-kit (NiosII Stratix kit) to
> > reconfigure repeatedly.
> >
> > How can I assign just one pin to drive high? I'm certain it can be
> > done, but for the life of me I cannot find the option in Quartus.
> > 
> > Thanks in advance,
> > Richard

> I have a VHDL design which I'm putting on an FPGA with Quartus II.
> There is a specific pin on the FPGA which I need to drive high. This
> pin has no corresponding port in my VHDL file and I don't want to edit
> the VHDL file.

Just out of curiousity, why don't you want to edit the VHDL file since 
apparently 'as it is now' the design is somewhat deficient in that it 
doesn't do what you want it to do.

KJ 

Subroto Datta wrote:
> The Unused Pin Option setting is in: Assignments
> Settings->Device->Device & Pin Options->Unused Pins.

Thanks Subroto.

Do you know why this isn't the default?

Regards,
Tommy

The choice of unused pins driving low was used I believe to improve signal 
integrity. However I am not an expert in this area, but I do know that 
several customers have mentioned this to be a confusing choice. The default 
will change with future device families.

- Subroto

"Tommy Thorn" <tommy.thorn@gmail.com> wrote in message 
news:1152662388.749655.119990@m73g2000cwd.googlegroups.com...
> Subroto Datta wrote:
>> The Unused Pin Option setting is in: Assignments
>> Settings->Device->Device & Pin Options->Unused Pins.
>
> Thanks Subroto.
>
> Do you know why this isn't the default?
>
> Regards,
> Tommy
> 

> Just out of curiousity, why don't you want to edit the VHDL file since
> apparently 'as it is now' the design is somewhat deficient in that it
> doesn't do what you want it to do.

The VHDL file is autogenerated, and I feel that editing it with
specifics about the precise target board is a hack. To me this should
reside in a separate file or be programmable via the GUI.

Subroto Datta wrote:
> The Unused Pin Option setting is in: Assignments
> Settings->Device->Device & Pin Options->Unused Pins.

Thanks Subroto, but like I said:

> > > I can find the option in Quartus to assign all unused pins to say
> > > "driving low." However I want to keep the default at "driving low"
> > > while assigning just this pin to "driving high."

It's not the default I'm looking for, but rather a setting for
individual pins to ovverride the default. To me it is unreasonable to
assume all unsed pins should have the same behaviour. It would make
more sense to allow the assignment editor to override the default for a
given pin.

Thanks for your reply,
Richard

> Richard, the fix for you problem is (from memory) to enter the general
> settings (assignments?) and change the pin default from "output driving
> ground" to "input tristated".  That should solve this problem
> completely.

Spot on! I don't know why I didn't think of doing this. There is
obviously an external pull-up resistor on that pin.

Thanks a ton Tommy, and thanks to everyone for the help!

Richard

>The VHDL file is autogenerated, and I feel that editing it with
>specifics about the precise target board is a hack. To me this should
>reside in a separate file or be programmable via the GUI.

If it's auto-generated, it can be auto-hacked.  Just write
a script in your favorite language to do whatever needs
doing and toss that into your Makefile.

(That's not to discourage easier solutions.  I'm just trying
to say that you shouldn't avoid hacking the "source"
code because you don't think of it as source code.

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