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Altera_Forum's avatar
Altera_Forum
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12 years ago

Register lost fan-out -- how to find it by visual inspection

Hi everyone

I have a project with several entities and each one is already working separately.

Now i've tried to put all of them together but I am getting lost fan-out error. I know

that is probably because I forgot to connect some stuff. Now my problem: how can I

find out what I forgot to connect?

I am looking for something like rtl viewer, but that shows only the elements that were

generated during synthesis so I can have a tip on what I've forgot to connect.

I've inspected my code several times and I have no clue what I am missing.

Thanks in advance!

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    Anything that lost fanout during synthesis will be removed, so you wont be able to find it in the RTL viewer or anything similar. You may be able to find it in the node finder under the category "design: all names", but it wont show you any heirarchy.

    It should tell you what lots fanout during synthesis in the warnings, so you should be able to find it that way.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    is it error or warning?

    usually you get it as warning and is due to due optimisation, there may be nothing wrong here.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    12 years ago

    So there's no way? Thanks for the anwser

    I was able to find why I was getting fan-out. It happened that my project access a block ram and it was unitialized and it was

    always emitting zero values. Some pins get stucked at gnd and consequently the others lost their fan-out.

    I was lucky to find this error, because I would never thought that it would optimize away because of block ram.