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Strange error in Quartus II 3.0

Started by Panic October 21, 2003
After searching for the source of an error for quite a long time, I've
decided that I need some help, and once again you guys drew the shortest
straw ;-)

I have a 8 bit DFF with output q[7..0]. This feeds the net
dff_inst23_out[7..0]. (The reason this net is given this name, was to see if
the error actually was located where I thought it was, since the original
error pointed to some temp net.) Both the DFF output and the net is 8 bits
wide, and still I get this error message:

Error: Net dff_inst23_out[6] cannot be assigned more than one value
 Error: Net is fed by std_8bit_dff0:inst8|lpm_ff:lpm_ff_component|dffs[6]
 Error: Net is fed by std_8bit_dff0:inst9|lpm_ff:lpm_ff_component|dffs[6]
 Error: Net is fed by std_8bit_dff0:inst23|lpm_ff:lpm_ff_component|dffs[6]

This is repeated for each bit of dff_inst23_out.

Ok, so I have two other registers that feed this net, but they are not
connected! I understand that this is happening because the output of these
other registers are the same as the inst23 one, but hey, I've got more
registers like that, all over the place! So why is this happening to this
particular net?

I've taken a screenshot of the design in question, and my troublesome net is
the blue stub:
http://www.battlefield.no/bilder/inst23.gif

Any suggestions would be appreaciated!
Sincerely
-"Panic"



This looks like a bug. Panic, please email me the qar file for your project,
and I will take a look. In the meantime try replacing the lpm_ff with a dff
primitive and see if it makes a difference.

- Subroto Datta
Altera Corp.

"Panic" <panic74@hotmail.com> wrote in message
news:cUglb.518$mf2.4092@news4.e.nsc.no...
> After searching for the source of an error for quite a long time, I've > decided that I need some help, and once again you guys drew the shortest > straw ;-) > > I have a 8 bit DFF with output q[7..0]. This feeds the net > dff_inst23_out[7..0]. (The reason this net is given this name, was to see
if
> the error actually was located where I thought it was, since the original > error pointed to some temp net.) Both the DFF output and the net is 8 bits > wide, and still I get this error message: > > Error: Net dff_inst23_out[6] cannot be assigned more than one value > Error: Net is fed by std_8bit_dff0:inst8|lpm_ff:lpm_ff_component|dffs[6] > Error: Net is fed by std_8bit_dff0:inst9|lpm_ff:lpm_ff_component|dffs[6] > Error: Net is fed by std_8bit_dff0:inst23|lpm_ff:lpm_ff_component|dffs[6] > > This is repeated for each bit of dff_inst23_out. > > Ok, so I have two other registers that feed this net, but they are not > connected! I understand that this is happening because the output of these > other registers are the same as the inst23 one, but hey, I've got more > registers like that, all over the place! So why is this happening to this > particular net? > > I've taken a screenshot of the design in question, and my troublesome net
is
> the blue stub: > http://www.battlefield.no/bilder/inst23.gif > > Any suggestions would be appreaciated! > Sincerely > -"Panic" > > >
"Panic" <panic74@hotmail.com> wrote in message news:<cUglb.518$mf2.4092@news4.e.nsc.no>...
> After searching for the source of an error for quite a long time, I've > decided that I need some help, and once again you guys drew the shortest > straw ;-) > > I have a 8 bit DFF with output q[7..0]. This feeds the net > dff_inst23_out[7..0]. (The reason this net is given this name, was to see if > the error actually was located where I thought it was, since the original > error pointed to some temp net.) Both the DFF output and the net is 8 bits > wide, and still I get this error message: > > Error: Net dff_inst23_out[6] cannot be assigned more than one value > Error: Net is fed by std_8bit_dff0:inst8|lpm_ff:lpm_ff_component|dffs[6] > Error: Net is fed by std_8bit_dff0:inst9|lpm_ff:lpm_ff_component|dffs[6] > Error: Net is fed by std_8bit_dff0:inst23|lpm_ff:lpm_ff_component|dffs[6] > > This is repeated for each bit of dff_inst23_out. > > Ok, so I have two other registers that feed this net, but they are not > connected! I understand that this is happening because the output of these > other registers are the same as the inst23 one, but hey, I've got more > registers like that, all over the place! So why is this happening to this > particular net? > > I've taken a screenshot of the design in question, and my troublesome net is > the blue stub: > http://www.battlefield.no/bilder/inst23.gif > > Any suggestions would be appreaciated! > Sincerely > -"Panic"
Sounds like you shorted several outputs together. Given the error messages, you should check if your instantiations of std_8bit_dff0:inst8|lpm_ff:lpm_ff_component|dffs[6] etc. are correct. It looks like you assigned several of them the same output node. Vaughn Altera
"Subroto Datta" <sdatta@altera.com> wrote in message
news:yEllb.6749$aZ.1431@newssvr17.news.prodigy.com...
> This looks like a bug. Panic, please email me the qar file for your
project,
> and I will take a look. In the meantime try replacing the lpm_ff with a
dff
> primitive and see if it makes a difference.
I tried to use dff primitives for all the three std_8bit_dffs (lpm_dff) that fed the troublesome net in question, but that didn't change anything. I also tried to remove all the lmf_dffs and the net stubs closest to them, and insert new ones, but that didn't help either. (Not that I tought it would...but you never know...) What's so strange is that I have another design that is more or less equal to this, only without the four 8 bit key inputs and four 8 bit xors, but the section of the design that causes me trouble is totally alike between the two designs!
> Sounds like you shorted several outputs together.
Yes, somehow I must have done that. Or...Quartus did anyway.
> Given the error messages, you should check if your instantiations of > std_8bit_dff0:inst8|lpm_ff:lpm_ff_component|dffs[6] etc. are correct.
How can I check this? (Have you looked at the image I posted in my OP?)
> It looks like you assigned several of them the same output node.
But how? Not physically. That clearly shows on the image.
"Panic" <panic74@hotmail.com> wrote in message news:<cUglb.518$mf2.4092@news4.e.nsc.no>...
> After searching for the source of an error for quite a long time, I've > decided that I need some help, and once again you guys drew the shortest > straw ;-) > > I have a 8 bit DFF with output q[7..0]. This feeds the net > dff_inst23_out[7..0]. (The reason this net is given this name, was to see if > the error actually was located where I thought it was, since the original > error pointed to some temp net.) Both the DFF output and the net is 8 bits > wide, and still I get this error message: > > Error: Net dff_inst23_out[6] cannot be assigned more than one value > Error: Net is fed by std_8bit_dff0:inst8|lpm_ff:lpm_ff_component|dffs[6] > Error: Net is fed by std_8bit_dff0:inst9|lpm_ff:lpm_ff_component|dffs[6] > Error: Net is fed by std_8bit_dff0:inst23|lpm_ff:lpm_ff_component|dffs[6] > > This is repeated for each bit of dff_inst23_out. > > Ok, so I have two other registers that feed this net, but they are not > connected! I understand that this is happening because the output of these > other registers are the same as the inst23 one, but hey, I've got more > registers like that, all over the place! So why is this happening to this > particular net? > > I've taken a screenshot of the design in question, and my troublesome net is > the blue stub: > http://www.battlefield.no/bilder/inst23.gif > > Any suggestions would be appreaciated! > Sincerely > -"Panic"
Panic, There is a connection error in the schematic that you provided me which is not evident from the bitmap posted on the web. The qar file with the schematics shows this problem. Two bitmaps have been posted to you, one circling the problem connection and the other one with the fix. - Subroto Datta Altera Corp.
Thanks a lot. That one had escaped me!