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[SOLVED] Ring oscillator desgin doesn't generate ring oscillator as wanted

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kahlenberg

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Hi,
I am desingning a ROPUF (Ring oscillator PUF), however, it is not generating enough NOT gates, It should generate 15 NOT gates and connect them in a chain,
I am attaching all code and generated schematic.
ro.PNG
As you can see, it generates only chain5, 6, 9, 10, 13 and 14, I dont know why it doesn't generate other NOT gates.
Could you please help me?
Thanks.
 

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  • PUF.7z
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my guess, without looking at your code, is that the gates are getting optimized out. You need to use some attribute like KEEP to prevent the synthesis tool from optimizing out the gates.

BTW, I am always a little leery of opening an attachment from someone I don't know. You might be better off just posting your code using the CODE tags. If your code is too long, then most people won't look at it anyway.
 
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    kahlenberg

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A quick search seems to indicate the attribute is supposed to be:
attribute keep : boolean;
attribute keep of chain: signal is true;

and not
attribute syn_keep: boolean;
attribute syn_keep of chain: signal is true;

as you currently have in your code.

- - - Updated - - -

barry, it's a 7-zip file with only *.VHD files.
 
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ads-ee said:
A quick search seems to indicate the attribute is supposed to be:
attribute keep : boolean;
attribute keep of chain: signal is true;

and not
attribute syn_keep: boolean;
attribute syn_keep of chain: signal is true;

as you currently have in your code.

- - - Updated - - -

barry, it's a 7-zip file with only *.VHD files.
Click to expand...

Thank you very much, that was the problem, now it generates 15 NOT gates as desired.
 

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