Simulation and Verification

[melika]

      hello,
i have this warning in ISE 10.1, but it does not write any signals that form a combinatorial loop??!!
how i can find that signals?
thanks.

WARNING Xst :2170 :the following signal(s) form a combinatorial loop:

[hgleamon1]

What does the synthesis report say for this unit sp_aes_ecb? There should be an .srp file in your project directory structure that gives a full synthesis breakdown of every unit that is synthesised.

Regards,

Howard

[melika]

thanks for your guidance,

as you can see in my attached image, I have compelete description of other "info" or "warning"  messages, only for this warning I do not have any description.

!!!

[hgleamon1]

Yes but after the tools have synthesised the units (code you have written, any blockboxes, etc.), XST will produce a report for each module, at every level of hierarchy. This report is text file.

I would therefore expect, in the directory structure that you are running the project in, for there to be a file named something like <your_unit_name>_xst.srp. Conduct a search for it if you cannot navigate straight to it.

Inside this file will be a more detailed description of what XST is doing when it synthesises your modules. Post the relevant messages (or attach the whole .srp file) if you don't understand what XST is saying.

Regards,

Howard

[melika]

thanks a lot hgleamon1,

I've found signals.  :))

[sushantm]

It seems you have declared result_d2(0) as signal but you have never used it in your code.

That is the reason it will get trimmed during the optimized process.

[bassman59]

You should post your code. The messages tell me you're trying to use loops and other software constructs in your code, and the results are not what you want.

[melika]

thanks for your guidance,

my code is structural based and I do not have software loops in it, but I have multiplexers.

warning 2170, is for input and output of my multiplexers, I have attached one of the warnings.

the  attached image shows the block diagram of units and multiplexers, and I have tried to show the warning signals in it.

units and multiplexers were port mapped together, and it's difficult for me to attached my code because the every units has different code.

Is this warning important ?

Thanks

[hgleamon1]

I don't really understand what your code is trying to do based on your diagram - I get the feeling that some information is missing. It does look like a rather large loop, though.

Personally, I consider all warnings to be important.

What happens when you simulate this code - do you get the behaviour you want and expect?

Regards,

Howard

[melika]

I have simulated it in ModelSim SE Plus 6.1b, and every thing is OK. 

I've attached all of warning 2170.

thanks